motors, drives & motion

Motors, Drives & Motion

eHANDBOOK

TABLE OF CONTENTSSmooth driving with linear motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Expert panel offers some design potholes to steer clear of

How will VSDs alter motor efficiency? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

New ideas for tying motors and variable-speed drives together for better control

Hydraulic muscle, as needed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39

Sometimes brute force is needed, and a little hydraulic knowledge

can get things moving in the right direction

Get motors rolling, and add feedback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Keep an ear out for electromagnetic interference and radio frequency interference

Smart control and drive integration fills the bill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Italy’s Goglio wins Smart Machines category in Best Future Machine Awards

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eHANDBOOK: Motors & Drives 2

High-Performance Specialty Motors & Application-Specific Motion Systems

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Smooth driving with linear motionNew ideas for tying motors and variable-speed drives together for better control

By Mike Bacidore, editor in chief

WHAT ARE SOME DESIGN PROBLEMS YOU HAVE SEEN THAT SHOULD BE AVOIDED WHEN IMPLEMENTING LINEAR MOTION?

Design issues can be the source of headaches, especially when you’re implementing linear

motion . The technology can bring accuracy and precision to many applications, but select-

ing components requires a bit of forethought . Our panel of industry experts discusses some

potholes to steer clear of .

BROC GRELLapplications engineer,

Nexen Group (www.nexengroup.com)

Designers forget to add the mass of the motor, gearbox and linear system to the mass that

needs to be moved by the linear system . Designers forget the cables will pull on the sys-

tem, as well . When going into an existing system as a retrofit, make sure there is room for

the new system and that it can be attached properly to the machine . Designers don’t un-

derstand how all the components—motor, gearbox—in the system add up to affect aspects

such as friction, inertia mismatch and total required force to move the system .

When using a software calculator system for motor sizing, it is the same old saying with a

hand calculator, where junk in equals junk out . Making sure the inertias are correct and being





located correctly through the different ratios

in the system and making sure drag is under-

stood are very important . A designer should

always look at the motor that the system

recommends and make sure that it makes

sense with the load and ratios in the system

before just running with that motor . Some-

times mistakes are made in the calculator

that can cost a lot of money if the motor is

extremely oversized or undersized because

of a mistype in one of these calculators .

MATT PRELLWITZmotion product specialist,

Beckhoff Automation

(www.beckhoff.com)

Before you start the implementation, you

need to be sure of the exact linear-motion

requirements in your application—distance,

load, mass, inertia—in addition to the limita-

tions of your components and controller .

This is a major reason why we suggest a

PC-based control system with the motion

handled in software, because it provides the

ability to more easily scale your controller

as the needs of your application grow and

change . In addition, choosing robust com-

ponents, with the help of motion-configu-

ration software, will go a long way to avoid

future mechanical failures or underwhelm-

ing performance .

GARY ROSENGRENdirector of engineering,

Tolomatic (www.tolomatic.com)

As it pertains to linear actuators, not con-

sidering the effects of resulting moments, or

torques, the position and size of the load on

the cylinder determines the resulting bend-

ing moments applied to the cylinder itself .

Even if a load is located on and directly

over the center of the load-carrying device,

it will still be subjected to bending moments

on acceleration . It is important to determine

if the cylinder is capable of handling the

resulting moments . For off-center or side

loads, determine the distance from the cen-

ter of mass of the load being carried to the

center of the cylinder’s load-carrying device

and calculate the resulting bending moment

(Figure 1) .

Don’t overlook the effects of dynamic mo-

ment loading . Unlike rod-style actuators,

many rodless actuators must support the

load during acceleration and deceleration

at each end of stroke . When there are side

or overhung loads, the dynamic moments

must be calculated to determine which rod-

less actuator is best equipped to handle the

resulting forces .

Remember to account for forces which

occur during motion—dynamic forces—par-

ticularity those which occur at the point of

acceleration or deceleration . These forces

acting upon the bearing system may over-

come the capability of the bearing system

and shorten life .

When an actuator is mounted vertically in

an application, additional force and load



air considerations must be addressed . An

actuator mounted vertically needs to over-

come the force of gravity first before it

can accelerate a load upward . A vertically

mounted cylinder will need to produce

more force than a horizontally oriented cyl-

inder to achieve this .

Oversizing actuators is a bad habit left over

from fluid power applications where over-

sizing was considered inexpensive insur-

ance against not having enough power .

With fluid power cylinders, the additional

cost of a slightly larger actuator than nec-

essary was minor compared to the extra

engineering time that might be involved in

sizing it correctly . It was common for engi-

neers to build in a 2:1 safety factor on fluid-

power applications for a variety of reasons .

These included erring on the conservative

side to compensate for imprecise knowl-

edge of the loads, fluctuations in available

air pressure and oversizing in anticipation of

higher loads in the future due to production

growth or application changes . Electric ac-

tuators can cost significantly more up front,

so over-sizing is a more costly mistake .

The environment in which the actuator will

be operating can have a profound effect on

PRECIOUS MOMENTSFigure 1: Mx Moment (roll) is created by loads applied at a distance from the x axis. My Moment (pitch) is created by loads applied at a distance from the y axis. Mz Moment (yaw) is created by loads applied at a distance from the z axis.(Source: Tolomatic)



performance, durability and maintenance .

High temperatures can affect seals, lubrica-

tion, bearings and motor life . Extremely low

temperatures can also affect performance,

lubrication and wear . Contamination with

oil, water or abrasive grit can destroy seals

unless the actuator has an appropriate IP

rating . Since IP ratings only address static

conditions, dynamic conditions such as

vibration, heat, cold or movement also have

to be considered .

Rod-style actuators, characterized by the

piston rod or actuator rod extending and

retracting with each cycle, typically of-

fer numerous mounting options . Mounting

options such as drilled and tapped holes

in the device, mounting feet, spherical

rod joints, alignment couplers, clevises or

trunnions are commonly offered by most

suppliers of rod-style actuators . When

employed with a guided mechanism, care

must be exercised to assure each subsys-

tem, actuator and guide assembly is capa-

ble of unimpeded, smooth motion . Systems

that attempt to rigidly couple the drive

element to the driven element may exhibit

inconsistent performance as these two

elements try to move in separate planes

with one or both of the subsystems loaded

beyond its capability .

A rod-style actuator in such a system is

best employed with some compliance

member between the drive member—ac-

tuator—and the driven—guide system . For

example, a spherical rod end mounted

to the actuator rod allows the mounting

point to swivel about the spherical joint .

This type of connection at the guide is

best used in conjunction with a trunnion or

clevis at the opposite end of the actuator

where it attaches to the machinery frame

element . Such a mounting scheme allows

compliance in the connection without add-

ing undue stress to either the drive—actua-

tor—or the driven—guide system .

Rodless style actuators, characterized by

their strokes being contained within their

overall lengths, may also contain a guide

system built into the actuator . Rodless

actuators, when used in conjunction with

a separate guide system, as I mentioned,

will also need to include a compliant

member in the connection between the

drive and driven members . Most actuator

suppliers offer a variety of mounts in-

tended for this type of installation, such as

floating brackets .

Rodless actuators that include a guide

system can perform the task of guiding

and supporting the equipment while taking

the place of a separate guide system . This

feature can be particularly useful and many

times saves the machinery builder time and

money in the process . Rodless actuators

with integral guides can be built into the

machinery in combinations to meet a wide



variety of motion needs . Multi-axis con-

figurations such as x-y or x-y-z along with

gantry configurations are all possible with

proper sizing . In the installation of rodless

actuators with integral guides, alignment is

equally important .

When mounting an actuator or a series of

actuators to a structure you must consider

parallelism and perpendicularity . Parallel

misalignment can apply an unfavorable

Mx-axis bending moment on the bear-

ing system . Carriages of rodless actuators

must be mounted at the same height . They

also need to be mounted at a consistent

distance apart from each other from one

end to the other to prevent an unfavorable

Fy-axis side load on the bearing system

which can cause binding . In addition, they

need to be mounted level to each other to

prevent an unfavorable bending moment in

the My-axis on the bearing system .

Perpendicular misalignment in an x-y-z

system in the x plane applies an unfavorable

y-axis bending moment on the actuator’s

bearing system . In a gantry system where

two actuators are in the x-axis or y-axis,

they need to move simultaneously . Misalign-

ment or inadequate servo performance will

apply an undesirable bending moment in

the Mz-axis to the bearing system .

Actual tolerances related to alignment

recommendations and mounting vary

from actuator manufacturer to actuator

manufacturer, as well as from bearing

type to bearing type . However, a general

rule of thumb is to consider the bearing

system type . High-performance bearing

types such as profile rail systems tend

to be quite rigid, and alignment is more

critical . Medium-performance systems

using rollers or wheels often have clear-

ance which offers some forgiveness in

alignment . Plain bearing or sliding systems

often have greater clearance and may be

even more forgiving . When installing lin-

ear actuator mounting systems, there are

a number of measurement tools ranging

from gauges to laser systems . Whatever

tools are used, always create one axis as

a reference for the x-y and z planes and

mount the other devices with respect to

the reference axis . Doing so will help to

get the maximum performance and lon-

gest life from your actuator system .

BRIAN ZLOTORZYCKIEtel motors product specialist,

Heidenhain (www.heidenhain.com)

Make sure the motor being used is prop-

erly sized to avoid any overheating due

to the motor working close to its capac-

ity . To help alleviate any unwanted heat

generation, users can dissipate the heat

through an external cooling method, such

as a heat sink, or increase its size . Also,

the tolerances of the air gap need to be

maintained . The standard gap is typically



0 .9 mm, and, if it increases, then the per-

formance of the motor suffers .

CLINT HAYESproduct sales manager,

linear motion technology,

Bosch Rexroth (www.boschrexroth-us.com)

Not accounting for full loading condi-

tions—mass load, tooling or process

forces—results in undersized components

for the application . Not achieving the re-

quired degree of precision results typically

from a poor understanding of the differ-

ence between travel accuracy, repeatabil-

ity and positional accuracy . Oversizing of

bearings—build to perception—can result

in missing the required price points for

the market . And there’s not accounting

for environmental impact on the life of the

bearings—humidity, washdown require-

ments and contamination .

Rexroth uses the acronym LOSTPED as a

way to remember all critical factors in de-

signing linear motion systems: load, orienta-

tion, speed, travel, precision, environment,

and duty cycle .

DERRICK STACEYsolutions engineer,

B&R Industrial Automation

(www.br-automation.com)

Alignment of the load bearing elements

is crucial . Most linear motors, including all

electrical, as well as ball screw and belt type,

are designed to provide higher thrust force

than the load they are physically able to

carry, so they are often coupled with load-

bearing elements . This can be recirculated

ball guides or roller bearings among others .

Ensuring that you have enough overhead to

handle the load is important, but in the end

we need to be able to smoothly and control-

lably move from A to B .

Designers need to take into account that the

higher the precision and load capabilities of a

linear bearing usually mean a loss of flexibility

and misalignment tolerance . This lack of flex-

ibility often leads to control/tuning issues that

can yield delays or performance degradation

of the overall system . By keeping this in mind

from the start, these downstream issues can

be minimized or even avoided .

CHRIS BULLOCKapplications engineer I,

Bishop-Wisecarver Group

(www.bwc.com)

Not including proper lubrication systems

is, by far, the most common . The next is

trying to design a machine without having

adequately determined the system require-

ments . Never purchase until you figure out

exactly what needs to be done by the ma-

chine and how .



JOSH TESLOWapplications engineer,

Curtiss-Wright

(www.curtisswright.com)

One age-old issue is machine-tool program-

mers guessing the user units during initial

programming and crashing servo mecha-

nisms the first time they push the start but-

ton . It is so important to double-check all

parameters/user units before test-running

expensive equipment .

There tends to be a strong focus on the

mechanical portion when sizing a system

and not enough focus on the controls . The

controls, especially the programming, are

just as important as the mechanics . The me-

chanical portion will only do what it’s told .

Different types of misalignment can occur

during installation or operation . The load

must be properly guided, whether that’s

with the actuator or some kind of external

guide . It must be properly guided when

long life or high force is required .

JAY JOHNSONnational product manager,

Sick (www.sickusa.com)

Linear motion is a wide scope, so I’ll focus

this response to a problem that may arise

with the addition of a linear feedback de-

vice to a rotary servo motor driven axis .

Ball screw or belt driven linear axes typi-

cally have compliance and/or backlash,

and it increases with use as the mechani-

cal components wear . In addition, there

will be some degree of non-linearity in the

manufacturing and assembly of the drive

components . Therefore, in applications

requiring high positioning accuracy and

repeatability, it may be necessary to add

a linear encoder to close the position loop

while the motor mounted encoder is used

for speed control and commutation . With

this addition, the system is now positioning

to the linear encoder, eliminating the vari-

ability of the ball screw grind accuracy or

linear bearing alignment .

In this scenario a new problem can be in-

troduced depending on the control scheme

and how much compliance is in the me-

chanical system . Consider that when an

axis is enabled and holding position, there

may be external forces such as a cutting

tool or gravity in a z-oriented axis . The axis

will move slightly from the pressure, and so

will the linear encoder . The encoder signals

this movement, and the controller sends a

corrective signal to the drive amplifier . Yes,

this is normal PID loop behavior, but the

problem comes if the lost motion is large

enough that the corrective move doesn’t

complete quickly . For instance, if there is

.003 inch of backlash in a ball screw and



the axis is loaded to one side, the position

feedback will be delayed while the slack is

being taken up . With typical gain settings,

the control will quickly react with a stronger

corrective signal because the feedback isn’t

changing . Now the axis is traveling faster

and it moves slightly past the target posi-

tion . The control immediately reverses the

signal to correct, but again the lost motion

must be taken up . A hunting effect can be-

gin resulting in an axis continuously revers-

ing in an attempt to close the position loop .

This problem is magnified in systems with

high stiction such as with large machine

tools or heavy moveable structures .

One solution is to lower the system gain

so that the controller doesn’t respond too

harshly, but this may not be practical for

the application as it softens the overall

performance . Another option is to increase

the feedback resolution, but this will only

help but not eliminate the problem . Some

motion controllers are able to effectively

deal with this issue, especially in the CNC in-

dustry . Methods include different gain and

acc/dec settings for commanded moves

versus holding position, or the use of me-

chanical clamps during idle/holding opera-

tions . Obviously, the best synopsis is to re-

duce the backlash to a minimum if possible .

http://www.c-flex.com

http://www.beckhoffautomation.com/AX8000

A Control Design reader writes: As part of a spare-parts readiness and moderniza-

tion initiative at our material processing and packaging plant, I have inventoried

more than 140 motors in our facility from sub-horsepower to 100 hp, and there are

many more . After a preliminary analysis, my manager wants me to include opportunities to

advance our green initiative, as well .

I need to identify plant-modernization projects to improve motor efficiencies . This in-

cludes updating motor-control design by adding variable speed drives (VSDs) where ap-

plicable . To start, any suggestions on integrating a controller or PLC to a VSD and motor

are appreciated .

Additionally, I am having a hard time understanding which motor applications would benefit

from use of a VSD . I think fans and pumps would definitely benefit, but I’m not sure how to

make that decision . How do I know if adding a VSD to a fan, conveyor, agitator, mixer or

rock crusher has efficiency benefits? How is the decision made? Does size matter?

I also have several process lines with six or more motors each, all running conveyors, agita-

tors and mixers at full speed to process or convert materials . Sometimes we could just run

half speed or a set-point speed, depending on demand . Some things I can slow down, and

some things I cannot . How do I tie all the motors and drives together for better control?

How will VSDs alter motor efficiency?New ideas for tying motors and variable-speed drives together for better control

By Mike Bacidore, editor in chief





ANSWERSTHE SOFT STARTIdeally, you would start by installing soft

starts on most large motors . A soft start

is a VFD hybrid with a bypass across-the-

line contactor that ramps up motors to the

across-the-line speed and then closes the

across-the-line contactor to take the ramp-

ing module off-line . Next, keep in mind that

for every VFD you install, you will have to

also stock an equivalent VFD unit and that

the shelf life of a VFD is relatively short—

six months—until it needs maintenance

to polarize the drive . Installing a replace-

ment VFD that has not been polarized in

more than a year will oftentimes cause it to

explode . From an overall kindness to your

stocking room and its shelf space, I would

only consider VFDs on those motors that

can directly benefit for other reasons than

a green initiative . A soft-start module will

keep your power factor in a much better

state and result in less peak demand on

your utility, especially around shift change,

and they are simple to retrofit, assuming

you have panelboard space . For smaller

motors, say less than 10 hp, the case for a

soft start is hard to make .

Back in the day, we used to tie a whole con-

veyor-line section together using a single

VFD in Volts-Hertz mode . We would have a

large VFD that would have several across-

the-line motor starters on the secondary

side of it, each one feeding a different

motor . You could change the drive speed,

and all of the motors would change speed

together in perfect synchronization, almost

like they were electronically geared togeth-

er . Using this old-school method does not

utilize the newer drive modes like sensor-

less vector mode, so the drive is a little less

efficient, but you can add a dynamic brak-

ing module to the main drive, and you can

gain braking capability on multiple motors

at the same time with one module .

Doug Taylor, principal engineer / Concept Systems /

www .conceptsystemsinc .com / member of Control Sys-

tem Integrators Association (CSIA, www .controlsys .org)

VARIABLE SPEEDThis is a very big subject, but it’s very rel-

evant to modern technology . What applica-

tions are good ones for applying a variable

speed drive? In the old days, the acronym

VSD meant variable speed device and also

included such devices as adjustable gear-

boxes, belt shifters, wound rotor motors,

eddy current clutches and anything else that

could affect speed . To avoid any confusion,

I’ll use the acronym VFD, if you don’t mind .

Generally, any application that requires the

speed to be changed over time is a good ap-

plication . An example of a VFD application is

the supply and exhaust fans for air handlers .

The old way was to operate a fan motor at

full speed and have a damper operator that

opens and closes to vary the air flow . This is

very inefficient since the motor load stays

high even when the damper is closed . The



VFD is a perfect fit for this application . The

damper is removed or blocked wide open,

and now the speed of the fan is directly

controlled by the VFD which controls the air

flow . This reduces the load on the motor at

lower speeds . There are many utilities across

the United States that will help to pay for

adding VFDs to these types of applications

because of the energy savings . The best ap-

plications for saving are the ones that have

the biggest speed change from minimum to

maximum . If you run above 80% speed at

all times, it might not be worth it strictly on

energy savings .

Typical applications include fans, pumps,

conveyors, agitators, mixers, coordinated

drives and elevators .

Motors that run at a fixed speed all the time

should have gearboxes to make sure the mo-

tor is running near rated load at rated speed .

Many people oversize fixed-speed applica-

tions because they think, if they need 15 hp,

then 20 hp is better . The mistake is that each

motor draws reactive as well as real power

to run, and, if you continually oversize the

motors in a facility, it can affect the power

factor and cause increased utility costs .

Regarding integration of VFDs with PLCs

or other controllers, manufacturers these

days are making their drives compatible

with many different control systems . Most

have Ethernet ports on them for communi-

cations to PLCs directly . All the major PLC

manufacturers that sell both PLCs and drives

already have a straightforward way to get all

the drives communicating over the Ethernet

network for start/stop, forward/reverse and

speed set point . In your case, if you have any

existing drives that do not have communica-

tion ports available, it is usually easy to just

hardwire from the PLC outputs to the drive

inputs for the same type of controls that you

can do over Ethernet in the newer drives .

Once you have control over the starting,

stopping and the speed set point for a drive,

the control becomes fairly straightforward .

For the motors without VFDs, you’ll need

to consider adding them . Be aware of a few

things that can trip you up .

The ac “across the line” motors are full-

voltage non-reversing (FVNR) motors and

can regenerate back into the ac line for

overhauling loads . The VFDs do not accept

regenerative energy very well unless you

add what is called a dynamic braking resis-

tor or have a line-regen ac drive .

The dynamic braking resistor generally

connects to specific terminals on the drive

called BRK+ and BRK- . The purpose of the

dynamic brake resistor is to absorb the

energy created by an overhauling load . That

is a load that causes the motor to actually

run faster than the called-for speed you are

running at . For example, if you want a large

fan to stop quickly by asking the VFD to

stay connected and to decelerate rapidly,

the inertia of the fan keeps it spinning . This



causes the VFD dc bus voltage to begin to

rise . If something isn’t done in this instance,

the voltage will eventually go high enough

to trip the drive on overvoltage . With dy-

namic braking, the energy from the dc bus

is dissipated as heat in the braking resistor,

and the fan slows more quickly while the

dc-bus voltage is maintained at a safe level .

The ac drives can run at frequencies much

higher than the normal nameplate of the

motor . It is not unusual to run a VFD up to

90 Hz in some applications . With increased

speed/frequency you have to remember

that, above 60 Hz, your horsepower stays

constant but your available torque drops

off . To compensate, the motor must draw

more Amps to stay at the correct speed .

The general rule of thumb for liquid pumps

is the horsepower requirement goes up as a

square of the speed, while, for an air fan, the

horsepower goes up as a cube of the speed .

So be careful about sizing your motor and

drive, if you intend to use the extended

speed range .

Scott L . Kinney, P .E . / electrical engineer / Taurus Power

/ www .tauruspower .com / member of Control System

Integrators Association (www .controlsys .org)

BELOW 100%If a motor will always run at 100% speed,

there is no benefit to driving it from a vari-

able frequency drive (VFD) above putting it

on a soft starter . However, if a motor could

perform the required task running well be-

low 100% speed much of the time, a VFD is

probably worth getting . This is true even if

other throttling equipment, such as valves

or dampers, must also be retained .

Variable frequency drives are more accu-

rate and repeatable than valves or dampers

and do not suffer from hysteresis

Variable frequency drives are more efficient .

Power is proportional to flow multiplied by

pressure; slowing a pump or fan and opening

a valve or damper means the same flow may

be achieved with less change in pressure .

Savings can be significant, often less than

half the power used with full-speed motors .

Variable frequency drives reduce wear on

ducts, pipes, valves and dampers caused by

excessive pressure drop . Variable frequency

drives may be oversped—above 60 Hz—to

increase the capacity of undersized equip-

ment . Variable frequency drives reduce the

strain on rotating parts during starts, extend-

ing life and reducing maintenance cost . And

variable frequency drives draw lower amper-

ages during starts, reducing peak loads and

voltage sag on switchgear . More operational

data about the motor is available without ad-

ditional instrumentation . A soft start has the

last three advantages, but not the others .

If a motor could be run below 100% speed,

it becomes a payback period question .

How long will it take for the savings from

improved control, reduced power consump-

tion and reduced maintenance to surpass



the cost of purchasing and installing the

VFD . That calculation is beyond the scope

of a brief response, but it’s usually less than

two years, and often well under a year .

Size matters a little bit . Generally bigger

motors offer more energy savings relative to

the purchase and installation cost . Note that

most equipment has a minimum speed to

work properly . Integrated cooling fans and

bearings with slinger rings depend on motor

speed to work properly, so running too slow-

ly will result in damaged equipment . Pumps

benefit greatly from VFDs, but pumps dis-

charging into high-pressure headers often

must run 80-90% of full speed to move any

fluid at all . Running too slowly will cause the

pump to overheat . Pumps running in paral-

lel to the same header must be matched and

driven together . Base-loading one pump and

swinging another could easily result in one

pump handling all of the flow and the other

pump overheating . Read more about con-

trolling large variable-speed fans and pumps

at www .controldesign .com/vsfans .

As for integration, I greatly prefer a com-

munication link between PLC and VFDs to

hardwired controls . VFDs can be configured

to safely trip on loss of communication

with the PLC . Redundant device-level-ring

(DLR) communication is available on many

models . Safety circuits—from e-stops and

guard sensors—can be hardwired to dis-

crete inputs on VFDs to work in conjunction

with networked control . In addition, to run

command and feedback, as well as speed

reference, a communication link also gives

easy access to speed and Amp feedback

and many other parameters with no addi-

tional wiring, and it allows configuration of

the VFD from a networked laptop .

Again, motors that would always run full

speed might benefit from a soft starter, but

would not additionally benefit from a VFD .

Agitators and mixers certainly benefit from

running more slowly—less power usage and

maintenance, plus better control over mixing .

Some materials benefit from initially vigorous

mixing followed by slower mixing to maintain

homogeneity, while others benefit from ini-

tially slow mixing and gradually speeding up .

Conveyors can definitely benefit from VFDs .

When programming them, there are a few

things to keep in mind .

Ideally you control height of material on the

conveyor . If you are feeding slowly, run the

belt slowly . When feed speeds up, speed

up the belt . The pile height will therefore

remain consistent . This can be a huge help

if you have a control challenge maintaining

the level/weight of the equipment fed by

the conveyor . With constant speed convey-

ors, once material is fed onto the conveyor,

it’s committed . But with VFDs, you can see

a change in feed rate almost instantly at

the discharge end because the conveyors

speed up and slow down with the feeders .



Any conveyor can run at the same speed

or faster than the conveyor upstream, but

generally running a conveyor more slowly

than the one upstream will cause problems .

I’ve worked on some conveyor systems

where the first four or five are on VFDs, but

the last two are constant speed . That’s fine .

But there’s no point in putting a VFD on a

conveyor downstream of a constant speed

conveyor, unless the VFD conveyor spends

much of its time being fed from an alternate

variable speed source .

I normally control such a system by pro-

ducing a demand based on the destination

equipment, and run the feeders based on

the demand . Then each conveyor has an

auto/manual bias station with the up-

stream equipment as an input . It can either

follow the upstream equipment, or be set

to run a constant speed . If all the conveyor

speeds are in auto, they all accelerate and

decelerate with the feeder . To prevent ma-

terial problems, often I’ll allow only zero or

positive bias and force even manual speeds

up to the upstream speed unless a techni-

cian is logged in .

Consider the capacity of the conveyor and

motors . The limit on such motors is Amper-

age/torque . Many conveyors do not do well

below 40-50% of full speed, so their turn-

down is not very flexible .

Chris Hardy, senior controls engineer / Cross Integrated

Systems Group / www .crossisg .com / member of Control

System Integrators Association (www .controlsys .org)

CONSIDER SHELF LIFEThere are many considerations that drive

the decision to use a VFD to save energy .

Since there is more potential for saving en-

ergy on high-demand equipment, it would

be a good idea to index motors in terms of

the highest horsepower and length of oper-

ating time . For example, a 50-hp motor that

runs 24/7/365 will use more energy than a

100-hp motor that runs 8/5/288 . The best

strategy is to concentrate on these high-

energy consumers because that is where

one will get the biggest return for efficiency

improvements .

One of the first things to check is the cur-

rent motor loading . Many times a load is 10

hp and someone in the past put a 20-hp

motor on the application, just to be safe . So

now, even a high-efficiency motor running

at half load will be very inefficient . Attempt

to have the motor size the next standard

rating above the maximum anticipated load .

Then, the application will be running in the

high-efficiency range of the motor .

Then next thing to find out is if there are

any times the load can be run at reduced

speed . If it can’t, then move on to the next

project . Putting a VFD on an application

that always runs at 60 Hz speed will use

more energy . This is because of the losses

in the insulated-gate-bipolar-transistor

(IGBT) power semiconductors in the drive .

If the speed can be reduced, then there is

a good chance a VFD would be a good fit .



Essentially, an electric motor is a constant

torque device, so, as one reduces speed, the

energy usage also reduces .

Also, look at the load type . If the load is a

machine, chances are it is a constant-torque

load, and cutting the speed in half will cut

the energy usage in half . If the load is a

pump or fan, the loading is typically a cube

function and cutting the speed in half will

cut the energy usage by 7/8 . One needs to

pay attention to the duty cycle . If the time

spent at low speed is significant, the motor

cooling fan is ineffective at cooling the mo-

tor . An external fan may be needed . Invert-

er-rated motors will have a turndown ratio

specification indicating the lowest speed

the motor can run without adding an exter-

nal constant-speed blower .

Lastly, PLCs and other logic solvers, some-

times onboard the VFD, can be used to

monitor the system and decide when

speeds can be decreased or increased .

They can be used to set speeds based upon

recipes . They can be perhaps programmed

to turn off equipment when not being used .

They can be used to match line speeds . It is

common today for a drive to be controlled

over a fieldbus—EtherCAT, Modbus/TCP,

EtherNet/IP—connected right to a PLC . This

makes control easy .

If the application does not appear to be

suitable for a VFD, one can consider a

soft starter . A utility power bill always has

two components—an energy charge and a

demand charge . While a VFD affects both

because it can soft-start the load and re-

duce speed, the soft starter only affects the

demand charge . The soft starter will start a

motor direct on line (DOL) using semicon-

ductors to limit the starting current thereby

controlling the demand . When the motor is

up to speed, a bypass contactor will close,

shorting across the semiconductors . Be-

cause the motor current is shunted through

the contactor, there is no longer an energy

loss due to the current flowing through the

silicon-controlled rectifiers (SCRs) .

One other thing to consider is that any

electronic product adds complexity to a

control system . VFDs and soft starters, be-

ing power electronics, are not as rugged

as a DOL starter . There will be equipment

failures . Most manufacturers will cover

the cost of the drive if it failed during the

warranty period . However, troubleshoot-

ing, removal and re-install are generally not

covered under a manufacturer’s warranty .

If the process is critical, one may want to

keep spares . Soft starters generally have a

long shelf life . Not so with VFDs . The VFD

problem centers around the electrolytic bus

capacitors that filter the dc bus . When the

drive is not powered, the electrolytes in the

caps will migrate out of position . If power is

off for less than a year, most modern caps

are OK . Between one and two years, migra-

tion has started . After two years, the bus

caps should be reformed . A good drives



service center can perform this procedure .

This problem is applicable to all VFDs with a

dc bus; every manufacturer has this prob-

lem . Needless to say, just because a drive

goes two years without power doesn’t

mean it will blow up . But it happens enough

that, if it is the only unit left that will get the

equipment running again, one should not

take the chance and opt to reform the caps .

The most successful upgrades are done

when the end user retains the services of a

reputable control system integrator (CSI)

experienced in the drives market . The CSI

will spend the time with the various appli-

cations and recommend the best compo-

nents for the particular application . Work-

ing with a vendor salesperson may work,

but then equipment recommendations will

consist of items they sell . For example, the

application in question may need precise

position control, and a vendor may only

have a PLC-based motion control that is

based upon velocity . Both solutions are

technically motion control, but only one

solution is right for the application .

Kenn Anderson, President / Nova Systems / www .nova-

systemsinc .com / member of Control System Integra-

tors Association (www .controlsys .org)

PLANTWIDE GOALSThere are many ways and philosophies to

perform plant-modernization projects that

include green initiatives . This can be diffi-

cult without a clear understanding of what

equipment exists and what the true end

goal is . I have more than 25 years of experi-

ence working in ammonia-refrigeration con-

trols with energy management along with

plantwide process-automation projects .

Some of the key items you are asking are

logical and looking down the correct path .

I’ll try and break down my thought process

on a project like this as best as I can, under-

standing that there are a lot of variables .

If the mindset and funding is the “total”

plant upgrade, I would start with picking

a foundation control system for the end

game, instead of adding little pieces and

parts as we slowly and methodically go

through the entire plant and upgrade the

equipment . The initial cost will be higher,

but the overall savings will more than pay

for it in the long run . Not to mention, the

end system will be easier to maintain and

expand as you go along . A good end result

always results with a well-executed plan .

Some base questions to ask:

• What is the big picture?

• How many motors in all?

• Are you wanting to track power utilization

for specific products or functions?

• Where are they located throughout the

plant?

• Can they be logically grouped into com-

mon power distribution points or product-

specific applications?

• Are there safety concerns with all or some

of the motors?

• Are there some loads that are critical and

some that are not?



• What motors can be run as truly variable

speed or can have multiple speed set points

• What kind of environment will the equip-

ment be in—hot, cold, humid, dry, classified?

• What platform do you want to be on—

Rockwell Automation, Siemens, Schneider

Electric?

• Do you want to collect any performance

data or have a centralized control of all the

equipment, such as an an operator room?

• Do you want any data reporting, remote

monitoring or remote service/access?

Let’s start with some assumptions . I would

design a core control system capable of

running all of my future needs or design

it to be easily expanded as I go through

the plant to meet my end goal . I person-

ally prefer Allen-Bradley, but Siemens and

Schneider both have more than enough ca-

pability to do the same thing . I would make

a determination if I need any redundancy in

my design to help to prevent unexpected

or unanticipated downtime . This primar-

ily includes processors and networks . I

would use an Ethernet-based network as

my communications backbone in any of

the platforms . I would also look at safety

concerns to determine if any of the motors

need to be controlled in a safe manner . For

example, if a mixer is readily accessible by

an operator, we would need to consider

designing the control of that mixer to a Cat .

3 level and utilize a delayed safety relay to

allow the mixer to make a controlled stop

versus a coast to stop .

I would start with a design/build of a cen-

tralized control system consisting of an

Allen-Bradley ControlLogix platform . I

would consider a large enough rack to

house multiple processors and network

cards to meet my end design goals . To keep

costs down, I would only put in the base

components I needed to start the project

and plan for additional components as more

of the plant came on line . I would include

redundant power supplies along with an

uninterruptible power supply (UPS) system

and surge protection for the main control

cabinet power . I would do some preliminary

network design and choose a Layer 3 man-

aged switch to be the central hub for my

networked groups . From there, I would look

at the entire plant and divide up the equip-

ment/motors in a logical grouping, either by

location or functionality or both .

For example, building ventilation, dust col-

lection and overall system utilities such as

chillers and fluid coolers may be one group;

process and production lines may be anoth-

er group, packaging and receiving may be

other groups . Or you could look at general

areas: shipping and receiving, production,

east side of building, northwest corner—

whatever makes logical sense to you and

your end-control and data-collection needs .

Once the plant is divided up, I would look

for centralized motor distribution points to

meet those needs, along with the estimated

full-load amperage (FLA) . Within each

group, I would determine my safety needs/



concerns and then identify each area as

phases of the overall project . Phase I would

be the design and build of the centralized

control and monitoring system along with

the first grouping of upgrades . I would then

designate and provide preliminary bud-

gets to the additional phases of the project

based upon budgeting needs and timing .

On motors that cannot be slowed down,

I would consider their overall horsepower

requirements; I would be less concerned

with small motors, unless they start and

stop frequently . On larger motors, I would

consider a soft start or variable frequency

drive (VFD) for any motor 20 hp or larger .

You may be able to work with your local

power company and get credits based upon

changing the across-the-line (ATL) start-

ers out with soft starts or VFDs . Typically,

the costs of VFDs are now below the cost

of soft starts once you get above 5-10 hp

when networked .

From there, I would design a panel to serve

as the motor control center (MCC) for these

motors, unless a true MCC is required to

meet serviceability requirements . Custom

MCCs can be designed and built but may

or may not be a little more costly than,

say, a Rockwell Automation IntelliCenter . It

all depends on the overall equipment and

negotiated pricing . Always force two ven-

dors to face off on pricing of MCCs; never let

one assume they are the only answer to the

project, even if they truly are . It’s the only

way you will get a fair price . A custom MCC

is nice, because you can design it and build

it to meet your exact needs . Otherwise, you

will be purchasing an off-the-shelf system

that has to be field-modified to meet your

specific needs, such as hardwired safety

interlock circuits and networking . If you go

with an off-the-shelf MCC design, I would

consider purchasing extra sections and emp-

ty buckets for future use . It will cost less to

purchase them with the main project than to

add them later . I would then design in a local

ControlLogix rack or Flex I/O rack to pick up

any local analog or discrete control needed

within the MCC or local area . For all other

motors in which true variable speed can be

implemented, I would use the Allen-Bradley

PowerFlex family of VFDs and design them

to be networked back to the centralized

control system along with the larger motor

sizes . I would then implement any interlock

safety wiring into the base design .

I would include all local control power

distribution and networking needs within

this local MCC . I would also consider a local

control display depending on the need for

local control of the equipment and whether

local hand/off/auto (HOA) or start/stop

control and indication exists or is not in

the base MCC design . I would include a

local power meter networked back to the

centralized control system so the overall

equipment power diagnostics can be moni-

tored and trended in the central control

system . If individual equipment information



is needed, it can be pulled from its asso-

ciated VFD or soft start . If an ATL status

is needed, local power monitors can be

added to pick up key components or areas

of components—a set of conveyor mo-

tors, for example—based upon the overall

design . If there is a need for grouping of

motors on a conveyor or fan grouping that

you would like to have variable, this can

be done, as long as the VFD is sized to the

overall FLA and not the overall hp; there is

a difference . There are also limits as to the

amount of motors that can be connected

to a single VFD in the manufacturer’s

specifications . This is typically limited to

a maximum of five motors . There is also

a typical maximum hp per motor, and all

motors must be identical in ratings . In the

past, we have found that running a 60-Hz

fan or mixing motors at or around 50 Hz

improves the overall amperage demand

on the units without decreasing the overall

performance . Of course, you would need

to look at the torque curves and perfor-

mance curves to see if this is accurate for

your application . I do want to point out

that with the consideration of adding so

many VFDs to a plant, one must really

consider installing line reactors on all the

VFDs to prevent harmonics issues and to

ensure proper installation . This includes

using properly rated VFD cable and poten-

tially load reactors based upon installation

distances . These little steps will help to

prevent premature failure of motors, VFDs

and upstream equipment .

Once everything is determined, you can

look at overall energy savings methods .

Control-wise, you can monitor the peak de-

mand of the entire plant along with the total

kW usage . Knowing your peak demand

charges and your kW usage, you can deter-

mine actual power bills . If you have equip-

ment that is not critical and can potentially

be shut down or scaled back, software can

be developed to allow for load shedding of

equipment based upon a maximum peak

demand set point . As the system sees peak

demand increasing to a preset threshold,

key equipment can be stopped or loads

reduced to curb the peak . A schedule can

be developed as priority lists and allow-

able limits on load shedding . As a simple

example, if a conditioned space is ideally 70

°F and there is a set load required to main-

tain that temperature but it is not critical,

the conditioning of that space can be shut

down or scaled back and the temperature

can be allowed to rise or fall depending on

the space . However, there may be a thresh-

old that it cannot get above 75 °F . As that

load shed is active, if the space reaches 75

°F, the equipment is restarted to prevent

further temperature rise . You can then set

up priority levels for load shedding . That

space may be a Priority 1 load shed, and you

may have another space or piece of equip-

ment as Priority 2 . If Priority 1 load shed

goes into effect and peak demand is still not

curbed after a preset amount of time or a

secondary limit, Priority 2 kicks in . You can

set up continuing levels to act in the same



manner, although we usually limit it to five

levels of load shed .

Another option to add to the list that

hasn’t been mentioned is power-factor cor-

rection . This can be done plantwide with a

central unit or individually at each motor .

Either way, significant power-bill reduc-

tions can be realized depending on the

plant and power company .

All in all, it really comes down to under-

standing the process, end goals and over-

all controllability one wants to have on

the overall facility . Once you know that, it

comes down to understanding whether or

not there is a true payback on the cost of

implementation—the return on investment

(ROI) . A lot of facilities that are produc-

tion-based really don’t have enough flexi-

bility in the system to allow for true energy

management, or at least not one that will

have a sufficient ROI . They may be able to

improve a few percentage points in overall

efficiency, but that may not relate into the

overall bottom line . In ammonia refrigera-

tion, we have found the most significant

implementation to be in cold-storage facili-

ties rather than production facilities . Pro-

duction facilities have a base demand that

cannot be modified without catastrophi-

cally affecting production, whereas cold-

storage facilities have functional limits that

can be manipulated to control a peak de-

mand . Other industries concentrate more

on understanding their costs by monitor-

ing specific aspects of their plants, such

as specific product lines or core utilities .

That way they have a better understand-

ing of where their costs are for accounting

purposes . Every customer is unique, and

every project is unique, both in the thought

process and in the needs . It’s always our

responsibility as an integrator to determine

what that is and meet their goals .

Bradly A . Johnson,vice president, maintenance services

division; vice president, industrial process group divi-

sion / Dilling Group / www .dillinggroup .com / mem-

ber of Control System Integrators Association (www .

controlsys .org)

STANDARD VS. CUSTOMRelative to the motor, we plot efficiency

curves for our motors (Figure 1) . Motor

efficiency peaks at approximately 4,300

rpm for this standard motor . If you had a

lower-speed application, we could cus-

tomize the winding so that peak efficiency

happens at a lower rpm . Figure 2 is the

same motor with custom winding, and

now peak efficiency is happening at ap-

proximately 2,700 rpm .

Here’s another way to describe it . Let’s

say your application required 2,700 rpm .

If you buy a motor that has a rated speed

of 4,300 rpm, you are not using all of the

speed that the motor can provide . How are

you paying for this? Essentially you now

have a voltage constant (V/Krpm) that is

too low, giving you more speed than you

need . With a lower voltage constant, you



also have a lower torque

constant (Nm/Amp), so you

need to provide more cur-

rent relative to the torque

that the application needs .

By designing the winding

more around the 2,300 rpm

requirement, your voltage

constant is more in line

with providing you only

with the speed you need .

So, in this example, you

could have a higher voltage

constant—less speed rela-

tive to voltage provided—

which would also give you

a higher torque constant—

less current for the torque

you require .

The motor is operating more

efficiently because there is

no speed or torque capabil-

ity that is sitting stagnant .

These types of modifications

can easily be made to a mo-

tor by changing the AWG

(American wire gauge) of

the copper and its number

of turns in the stator .

There are other things that

can be done to improve

overall efficiency relative

to heat dissipation via rotor

and stator design . But those

types of considerations are

usually looked at during ini-

tial product design and are

not something that would

be offered via a customiza-

tion to an existing motor .

Jeff Nazzaro, gearhead and motor

product manager / Parker Hannifin

/ www .parker .com

AFFINITY LAWSYou can certainly save

energy and improve effi-

ciency by integrating drives

with your motors . Pumps

and fans are great targets

STANDARD MOTORFigure 1: Motor efficiency peaks at approximately 4,300 rpm for this standard motor.

CUSTOM WINDINGFigure 2: The same motor with custom winding now has peak ef-ficiency happening at approximately 2,700 rpm.(Source: Parker Hannifin)



for energy savings if you can slow them

down and still perform the needed applica-

tion . You have indicated that is the case, so

here’s how it works .

Pumps are fans are considered variable-

torque (VT) loads . The valuable point here

is that VT loads follow the affinity laws,

which really make three points .

Flow (water, air) through a VT system var-

ies directly with the motor speed . So, if you

run the motor at 50% speed, you get 50%

of the flow through the pump or fan .

Pressure varies with the square of the mo-

tor speed .

Power, or energy consumed, varies with the

cube of the motor speed . So, if you could

run the motor at 50% speed, you would

only consume one-eighth of the energy .

Figure 3 depicts the affinity laws in a graph-

ical manner .

In fact, due to the cubic relationship of the

motor speed and the power consumed,

even slowing down the motor a small

amount can make a dramatic impact on

energy consumption .

SLOW THE MOTORFigure 4: Energy consumption is reduced by reducing motor speed on a VT (centrifugal pump or fan) load.(Source: Baldor Electric)

AFFINITY LAWSFigure 3: Due to the cubic relationship of the motor speed and the power consumed, even slowing down the motor a small amount can make a dramatic impact on energy consumption.(Source: Baldor Electric)



Figure 4 shows how much energy con-

sumption is reduced by reducing motor

speed on a VT (centrifugal pump or fan)

load . If you slow the motor down only 20%,

you will consume half of the energy .

The other applications you mention can

save energy, as well, if variable speed

drives (VSDs) are applied, but it will not be

the dramatic impact you will see with VT

loads, so I would recommend that you start

with your VT loads .

Integrating the motors and drives with the

PLC can be simple or complex . It largely

depends on the design of your system .

Integrating drives/motors with PLCs can be

done in a couple of ways:

• via digital and analog I/O modules on the

PLC backplane

• via industrial communication networks, such

as Ethernet/IP, Modbus/TCP, Profibus-DP .

If you do choose to integrate the motors

with a PLC, a program will also have to be

written to control the motors and drives .

The program could be quite simple or

quite complex, depending on what you are

trying to control . For the more complex

systems, you may want to consult with a

system integrator to provide you the func-

tionality you require .

Rick Kirkpatrick, product manager, ac variable speed

motors / Baldor Electric / www .baldor .com

MOTOR INTELLIGENCEThere are VFDs that have integrated com-

munications . Modbus RTU and Ethernet IP

are the most common communication for

process controls such as machines or con-

veyors and would communicate back to a

PLC . Modbus RTU, BACnet MSTP and BAC-

net IP are most commonly used for building

management systems that would tie in the

HVAC, pumping, lighting and fire systems

together for improved management . Most

VFDs have the ability to communicate these

protocols and have PC tools that allow for

easy commissioning and configuration to

the different networks . Application or com-

munication manuals would have all of the

bit numbers and descriptions for easy setup

and connectivity .

There are two different application where

VFDs can be used and provide the most

benefit:

1 . Any application where there is the oppor-

tunity for variable speed . These could be

constant-torque application (conveyors,

mixers) or variable torque applications

(fans, pumps) . Using a VFD to vary the

speed, rather than mechanical devices

such as a damper on a fan or a relay, you

improve the reliability of the system and

performance of the motor reducing any

losses . You also achieve reduced energy

usage, which in turn is reduced energy

cost . Many regulations are requiring VFDs



be used in variable-torque applications on

motors that are rated down to 5 hp . Title

24 in California, ASHRAE Standard 90 .1

and the 2017 DOE refrigeration legislation

are all examples of these regulations .

2 . Any application where you would like

to communicate status on a motor and

increase the protections of the motor . An

example would be a critical application or

pump . The VFD has built-in applications

and algorithms that can provide increased

protections on motors without the use of

additional sensors or external devices . The

list of protections can improve the life of

the system and provide feedback that will

help to predict when systems will fail and

reduce unplanned downtime .

There is an application built into some VFDs

that allows the VFD to be a master of other

VFDs or motor starters . This means that the

VFD can accept feedback from a demand

source—temperature sensor, pressure sensor,

speed reference from a PLC—and take that

feedback to control other drives or com-

municate back to other systems based on a

configured process . The communication ca-

pability increases the ability to get feedback

from all systems at once with alarms, alerts

and faults information with time stamps . This

increases the visibility of the system and

reduces unplanned downtime . It is all about

bringing the intelligence to the motor .

Nicole Angiola, product manager, HVAC variable fre-

quency drives / Eaton / www .eaton .com

ENERGY SAVINGSThis really depends upon the level of control

you require . If you are looking for a low-level

control with just speed set point, starting/

stopping and fault indication, this can be ac-

complished by simple I/O wiring with a few

discretes or optionally a few discretes and an

analog signal . If you want to be more precise

and/or if you will have a controller running

several drives, networking is a better way

to go . Ensure your PLC and the slave VSDs

support the same communication protocol .

Networking gets a lot of novice users intimi-

dated, but truly it shouldn’t . It’s very simple

with modern PLCs and drives .

Many, many applications greatly benefit

from the use of VFDs for energy efficiency .

Let’s start by looking at centrifugal pumps

and fans . Pumps and fans are sized for their

maximum duty point but usually are then

throttled down to a lower demand . Mechan-

ical controls such as guide vanes, bypasses

and throttle valves do present some energy

savings; however, the maximum efficiency is

gained by slowing down the motor directly .

These applications are referred to as variable

torque applications and are governed by the

affinity laws . In these applications the torque

required is a function of a square of the mo-

tor speed . The power required however is a

function of a cube of the speed . For example,

reducing the speed to 50% can reduce the

power required to 12 .5% of the rated power .



Modern VFDs can take ad-

vantage of this and reduce

the motor voltage appropri-

ately to gain those energy

savings at lower speeds to

follow the curves of the af-

finity laws (Figure 5) .

The simplest and least

precise is to have one drive

control multiple motors .

You need to check with

your drive manufacturer

if this is acceptable for its

drive to do this . In this ap-

proach you size the drive

for the sum total of all mo-

tors and provide an exter-

nal motor overload relay

to protect each individual

motor . Often drives cannot

be switched to/from load

without damage, so in this

approach you must often

select motor overloads that

have an auxiliary contact

that is break first/make

last, and you run those all

in series to a drive input

configured for external

fault—the idea being if one

of the motor overloads trip,

it first faults the drive and

doesn’t allow the drive to

be restarted unless all mo-

tor overloads are clear .

Another simple and still

imprecise way is to com-

mand speed to one drive

and then have that drive’s

analog output annunciate

its actual speed . Run that

analog in turn to the next

drive as its speed set point .

You can also use the drive’s

run/status output as a run/

stop command to the next

drive . It is imprecise, and it

is very basic . Error handling

of individual drives can be

an issue with this method .

Another approach that can

often be done—check with

your drive manufacturer—is

using a fieldbus such as

CANopen where the nodes

are peers and you would

have a master drive which

you command speed and

run stop to via its keypad or

control wiring, but then map

that master drive’s status

words on the network as the

command words to the slave

drives to have them follow

the master’s state . Precision

in this approach is a func-

tion of the motor control

method used by the drives .

Closed-loop vector is the

most precise . Open loop V/

Hz is the least . Error handling

of individual drives can be an

issue with this method .

A better way to do this is

networking the drives to a

REDUCED VOLTAGEFigure 5: Modern VFDs can reduce the motor voltage appropri-ately to gain those energy savings at lower speeds to follow the curves of the affinity laws.(Source: Lenze Americas)



PLC . The PLC can set speed

and control each drive and

also read each drive’s status

so faults can be annunciat-

ed and controlled reactions

easily set up to respond to

various conditions .

Joel Kahn, product manager, in-

verters / Lenze Americas /

www .lenze .com

ROI ANALYSISMany industrial plants

that are in the process

of implementing green

initiatives or moderniz-

ing to reduce costs must

evaluate the energy costs

associated with motors in

their plants . Motors tend

to play a large part in plant

efficiency and cost-reduc-

tion efforts because they

are usually responsible for

a substantial amount of

the monthly electric utility

costs . Some statistics indi-

cate that motors consume

70% of all domestic manu-

facturing energy and 55%

of total energy generated

in America . Interestingly,

most motors will consume

10 to 20 times their capi-

tal cost in energy every

year so any effort aimed at

reducing these costs can

yield significant savings .

In many applications where

motors are used to drive

pumps, fans or compres-

sors (centrifugal loads) and

are using throttling, either

valves or dampers to con-

trol the process flow or

pressure, variable frequency

drives (VFDs) may be ap-

plied to great economic

benefit . By changing con-

stant motor loads to vari-

able speed, payback ben-

efits may be realized in as

little as one to two years .

If you are reviewing your

plant for a modernization

initiative, reviewing the mo-

tors in the facility is a good

place to start since, in most

cases, they will represent

the bulk of your monthly

utility payment . If these mo-

tors drive centrifugal loads

like fans, pumps or com-

pressors and the process

operates below 100% flow

or pressure, there may be a

real opportunity for energy

cost reductions . The motors

are typically started with

motor starters .

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There are three charac-

teristics with centrifugal

loads known as affinity laws

that define the relationship

between shaft speed or the

speed your motor is running

and process parameters

such as flow, pressure and

power consumption .

• Flow (of material) is di-

rectly proportional to the

shaft speed .

• Differential pressure is di-

rectly proportional to the

square of shaft speed .

• Process power is directly

proportional to the cube

of shaft speed .

Therefore any plant pro-

cess that requires reduced

flow (air, water, oil, gas) can

utilize the affinity laws . For

example, if your process

is rated for a material flow

of 10,000 gallons/minute

(gpm) but can be operated

at a reduction to 7,000 gpm

or a 30% reduction in flow,

changing the motor speed

may yield impressive energy

savings . From the affin-

ity laws we know flow and

speed are directly propor-

tional, so if the motor speed

is reduced by 30%, the pro-

cess flow will also drop by

30% (10,000 gpm to 7,000

gpm), but the energy con-

sumption is a cubic function,

so the amount of energy

used drops even more; and,

in this case, a 30% reduction

in motor speed yields a 66%

reduction in energy usage .

This approach can also work

on many systems where

speed is adjusted such as

agitators, mixers, conveyors

and mills, and these typically

will also benefit from more

precise speed control .

As long as the plant pro-

cess is using a centrifugal

load that is being throttled

or controlled with dampers

or valves, it is likely that the

process can benefit from the

addition of a VFD . This argu-

ment applies for low-voltage

and medium-voltage mo-

tors . Other applications may

also benefit but may require

additional analysis and may

not yield the same energy

cost savings .

When evaluating a motor

system as a candidate for a

VFD, one should look at the

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turn-down speeds . As stated

above a 30% reduction of

speed yields large energy

cost savings . In processes

where the speed turn-down

rates are less than 90%, then

the viability and payback

of adding a VFD becomes

less clear . If the process runs

close to 100%, then the cost

savings of the VFD may be

minimal and possibly elimi-

nated by the efficiency of

the VFD itself . By adding

a VFD, the VFD itself has a

rated efficiency, typically

95% to 97%, and adds losses

to the overall system . The

savings associated with the

operating speed reduction

must be greater than the

efficiency losses of the VFD .

One note here is that there

is no such thing as a 98% or

99% efficient drive . These

numbers are bandied about

and usually represent only

the inverter section of the

VFD . Although they are true,

they represent only one sec-

tion of the entire system and

not the actual VFD compo-

nents required to run . Most

VFDs today operate with 3%

to 5% losses for the entire

VFD end to end . Sometimes,

input filters, sine wave filters

and output filters are not

included in this efficiency

rating as they are separate

from the VFD but are still

required . The VFD user must

be aware of all components

required to safely operate

the VFD to protect the plant

from unwanted harmonics

and to protect the motor

from insulation failure, har-

monics and bearing currents

leading to premature motor

bearing failures . The VFD

manufacturer should work

with you to develop a wire-

to-shaft overall efficiency

rating to clearly define the

actual losses and to identify

the installation requirements

for filters, additional cabling

connections and mounting

pads for various separate

components outside the

VFD cabinet .

In addition, most VFD manu-

facturers will work with the

process plant to identify the

potential costs savings and

generate ROI payback peri-

ods . These can include not

only the energy saving asso-

ciated with the VFD operat-

ing at reduced speeds but

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could include additional HVAC costs—addi-

tional control room air conditioning—but also

plant requirements like site arrangements .

There are several other advantages to in-

stalling VFDs on motors which are harder to

quantify but, nevertheless, very real advan-

tages . The use of a VFD eliminates the start-

ing inrush event that the motor experiences .

This has two advantages .

First, the elimination of the inrush current

when starting the motor, which can be six to

10 times the motor FLA rating, has the effect

of reducing the peak demand charges on

the monthly utility statement . Obviously, the

cost savings is dependent on the number of

motor starts but eliminating this phenom-

enon should have a positive cost impact on

reducing the peak demand charge on the

utility statement . Secondly, the elimination

of the inrush event dramatically reduces the

mechanical and electrical stress on the mo-

tor leading to longer motor life and lower

maintenance costs . However, this may be

negated by the selection of a VFD with an

inferior output waveform leading to har-

monic heating or insulation damage in the

motor, so care must be taken in the VFD

topology selection . The addition of output

filters to protect the motor leads to reduced

efficiency, which adds cost and possibly

plant power grid and safety issues (motor

self-excitation), which must be analyzed and

accounted for . These issues can easily be

overcome but may yield a longer payback

period, as well as additional operating ex-

penses if the plant power grid is changed .

Lastly, most modern VFDs will present a

constant power factor to plant power grid

of 0 .95 or greater, which will tend to reduce

the power factor penalty on the monthly

utility statement . This is a small charge and

is at most a secondary effect of the VFD .

However, care should be taken with older-

style current source drives where the power

factor is proportional to speed and can

become very poor when operating below

80% speed, potentially requiring the addi-

tion of power-factor correction components

in the plant . This adds installation costs and

possibly reduces efficiency, which again can

increase the anticipated payback period

and energy savings .

The discussion presented here applies to

low-voltage or medium-voltage motors and

their applications . Any VFD manufacturer

should be able to assist the end user, en-

gineering firm or electrical contractor with

the ROI analysis . Understanding the operat-

ing scenario and examining the plant single

line should be within the scope of the VFD

manufacturer’s expertise and part of the

proposal process . Additionally, the VFD

manufacturer should be able to evaluate the

plant motor, especially if it is an older, exist-

ing motor to verify proper operation and

motor life with the selected VFD .

Mark Harshman, director of system engineering / Sie-

mens / www .siemens .com



3 STEPS TO EFFICIENCY AND PAYBACKBlindly adding a VSD will not automatically

increase the efficiency of an axis (drivetrain

+ motor + VSD) . VSDs have power losses

and could worsen the overall system effi-

ciency . Determining efficiency increases and

fastest payback rates can be summarized

by the following generalized process .

1 . Does the application run at the motor’s “full

speed” and seldom start and stop? If the an-

swer is yes, then adding a VSD will hurt sys-

tem efficiency and simply add losses (VSD

losses and motor PWM heating) . Replacing

the motor with a higher efficiency version

is the best option . Determine if the motor

should be replaced now or later based on

current age of the motor, new motor cost

and energy savings payback rate . Fans and

pumps typically fall under this category .

2 . Does the application run at the motor’s

“full speed” but also starts and stops of-

ten? If the answer is yes, then a VSD can

reduce motor starting currents . The bigger

the motor, the more reduction in current

spikes (line start currents are typically six

times motor rated current) . The payback

rate is determined by how often the motor

starts and stops and how large the motor

is . You can also replace the motor with a

higher efficiency version, but check with

the VSD manufacturer . High-efficiency

motors may require an upsized drive due

to the low winding impedance .

3 . Would the application be better suited

running slower or faster than motor line

speed? If the answer is yes, then you

will need a VSD, or perhaps a gearbox

change, but be aware changing the

speed of the axis can affect required

torque and power . For example, saws

that run slower have dramatically higher

torque . Increasing fan speed increases

motor load quadratically and can be

mechanically dangerous .

If you are converting a whole line to vari-

able speed and it can mechanically handle

it, there are typically two control schemes:

velocity-follower and electronic gearing .

Velocity-follower systems can be thought of

as open loop controls running at 50% or 70%

speed . If an axis that is commanded to run

70% speed can run at 68% or 71% without

issue, then this type of control can be used .

In the olden days, the master axis would

have an analog output that was wired to the

analog input of the next axis . More modern

systems can use a fieldbus control and send

digital commands to each drive .

Electronic gearing is required for applica-

tions that have some type of registration—

closed loop, shaft lock . These are closed-

loop systems that can maintain shaft angle

relationships as if there was a mechanical

line shaft running the whole machine . It is

easiest to control these systems with a real-

time fieldbus like EtherCAT where each axis



can receive the master axis position over

the bus instead of running encoder cables

between each drive .

Scott Cunningham, product and application manager,

controls and automation / KEB America / www .ke-

bamerica .com

REDUCE COST, INCREASE CONTROLTo answer the first part of your question,

you should start by looking at applications

where there’s a need to control the speed

of the motor that is currently being con-

trolled by mechanics, a contactor for start-

ing and stopping or older variable-speed

drives . There are benefits that come with

using the variable-speed drive for starting

and controlling the application and ways to

improve not only the efficiencies of the ap-

plication and the way it’s running the motor,

but also the overall process . Product waste

is an area where improved control of the

motor and application can reduce product

or material waste, making the process and

the plant more efficient and saving costs .

Using a variable-speed drive, with or with-

out a PLC, in an application is accompanied

by significant benefits . Those include im-

proving the efficiency of the system, reduc-

ing waste, reducing maintenance cost and

having better control of the application . A

lot of times, people think that you’re just

adjusting the speed, but in reality you’re

reaping a lot more benefits than just having

variable speeds to run the motor at .

In terms of which motor applications would

benefit from a variable-speed drive, you need

to ask yourself, “Does the application run at

60 Hz?” That’s typically the base speed of a

motor in North America . If the motor is cur-

rently running at 60 Hz, day in and day out,

then the application may not benefit from

the variable-speed control but would benefit

when starting the motor and from the feed-

back the drive can provide on the application .

If it’s not running at 60 Hz because it’s being

adjusted by mechanics or other equipment

in the system, or if there’s a lot of starting

and stopping, those are the applications

where we would look at easily applying a

variable-speed drive . Any time you’re not

running at a base speed all of the time, if

there are any adjustments being made,

that’s where variable-speed drives help out .

Variable-speed drives provide precise speed

control . If you use a VSD, you can reduce the

inrush current when starting and the amount

of power to get things moving just by the

nature of using the variable-speed drive .

When it comes to tying all the motors and

drives together, you’re getting at the heart

of where variable-speed drives integrate

best in the process . Installing a VSD here

gives you the benefit of unlimited speed

points, so you can adjust speed to whatever

value you need for your application and co-

ordinate the movement of product . You can

also better control those applications and

eliminate any kind of waste .



There are two ways of going about control-

ling the process line, depending on how

much control is needed . There are settings

and application-specific setups within the

drive, as well as some additional program-

ming that can be dealt with . Drives handle

a number of different applications, so the

control can be as simple as being the de-

fault programming of the drive, configuring

the parameters to increase control of the

application while using the drive’s inputs

and outputs or going to a controller or PLC

to work with a number of different drives .

Using a controller or PLC to communicate

to drives and the different pieces of equip-

ment to control them and to receive the

data back can increase the number of drives

being controlled at one point all from a cen-

tral location . One of the major benefits of a

VSD is the data it collects . Not only are you

controlling the application, but you receive

information about the process and the ap-

plication . You can analyze how much power

you’ve been using and use the data you

receive to understand what’s going on in

the application and help you to identify any

issues to improve overall system efficiency .

Adding variable-speed drives to your ap-

plications can provide significant benefits in

terms of reducing waste and maintenance

costs, increasing control and improving ef-

ficiency across the board .

Jim Kluck, senior product marketing manager / Danfoss

Drives / drives .danfoss .us

ENERGY SAVINGSEfficiency is usually a derivative of cost up

front . This is where the interest of equip-

ment supplier and user can vary . Every

industrial application can be made more

efficient, so it generally comes down to

how much work it’s going to take, how

much money it will cost and when I can

expect the efficiency savings to pay back

the investment .

The first scenario for motors running across

the line is going to a more efficient motor .

Government regulations are mandating new

motors installed meet minimum efficiencies

that continue to increase . Today’s premium-

efficiency induction motors have a very

high efficiency, but motor manufacturers

are approaching the design limits to how

much more metal or copper they can put

into the motor to make them more efficient

before the frame size will increase .

The next scenario is changing a fixed-

speed application to a variable speed with

a variable-frequency drive (VFD) . For vari-

able-torque applications, such as a fan or

pump, this is typically a no-brainer as the

payback from energy savings is very short

if you can run at reduced speeds . A pre-

caution I would give is to verify the motor

is designed to be run from a VFD . There is

also an emerging trend for variable-speed

applications to use a synchronous motor

as they offer even higher efficiency with

smaller footprint .



There are also numerous VFDs and servo

drives that offer energy-saving functions and

configurations . A few typical functions are

ECO mode to reduce motor losses; bypass

mode to reduce inverter losses; and hiber-

nation mode to go into sleep mode during

long pauses . Since motors can generate

energy when stopping or with overhauling

loads such as cranes using drives that can

regenerate energy back to the power sup-

ply are preferred for certain applications . On

production machines with multiple drives a

common dc bus arrangement is very popular

to take advantage of energy sharing when

one or more motors are generating power

and other motors can utilize this power .

This is also a good time to mention that hy-

draulic and mechanical solutions are being

switched to electrical solutions due to the

high potential for energy savings . A hydrau-

lic pump with a fixed-speed application can

be replaced by a servo pump that supplies

energy only when required and can save

up to 70% the energy consumption . Even

replacing a gear box or pulley with a direct

drive can result in large increases in system

efficiency, so using a holistic approach to

energy savings is always best .

For payback calculations, I would use one

of the many free software tools available

from motor and drive manufacturers to help

to compare savings with different solutions

and help to validate the payback is expect-

ed on your investment .

Craig Nelson, senior product manager / Siemens Digital

Factory / www .siemens .com

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There is no doubt hydraulics has unmatched muscle, compared to pneumatics or

electrical power transmission in linear and rotary motion applications . While pneu-

matics may win the game when it comes to simple, low-cost and fast linear motion,

hydraulics has never been better .

Although many oil-leaking, hot, noisy hydraulic power units are still in service today, hy-

draulic technology has developed well over the years . Don’t let oil leaks from the past sway

your decision to use hydraulics . Leaks have been addressed and power units are quieter

making it a great option for some applications . New sealing technology has all but eliminat-

ed the puddles of oil under and around hydraulic devices . Fewer leaks also open the door

to higher operating pressures, and adding sound insulation in key locations has dramatically

lowered system noise, as well .

Check out a few basics on hydraulic systems and don’t reinvent the wheel when designing

and using this capable power transmission method . It does have its advantages .

In a closed system, Pascal’s law, which is the foundation of hydraulic drive systems, states

that the pressure anywhere is the same . Therefore, the force that the fluid transfers to the

surroundings is equal to pressure x area . The bigger the piston, the larger the force .

Hydraulic muscle, as neededSometimes brute force is needed, and a little hydraulic knowledge can get things moving in the right direction

By Dave Perkon, technical editor





Both pneumatic and hydraulic fluid-power

systems are used in a variety of industrial

machinery and off-highway equipment .

While pneumatics can transfer high force

and torque in power-transmission appli-

cations, it is often used in linear-motion

applications such as transferring, lifting,

clamping, gripping and stamping . These

applications are usually repetitive and fast

moving, as well .

It’s the heavy force and torque applica-

tions that benefit from the use of hydrau-

lic systems . These applications typically

involve tons of force such as pressing

metal, lifting large loads, digging or crush-

ing rock . While these hydraulic systems

eliminate many of the drives, gears,

chains, pulleys, drive shafts and ball

screws of an electrically driven system,

there are many fluid-power system com-

ponents that need to work together .

Considering the amount of power pro-

duced, hydraulic components are relatively

compact . It’s one of the reasons they’re

used in mobile construction and agricul-

tural equipment . A 5-hp hydraulic motor

could fit in the palm of your hand . It’s just a

fraction of the size of an equivalent combi-

nation gearbox and electric motor .

These hydraulic systems use an electrical

hydraulic power unit that includes an elec-

tric motor and hydraulic pump to supply

fluid power to the system . The power unit

also includes supporting equipment, such as

hydraulic reservoirs, heat exchangers, filters

and manifolds . It’s the hydraulic version of

an air compressor .

The pumping device, the prime mover that

converts mechanical power into hydraulic

energy, is often called an electric hydrau-

lic power unit . Unless you are an hydraulic

distributor or a fluid power expert, it’s best

to purchase this power unit assembled as a

system . Piecing an hydraulic prime mover

together takes some expertise and proper

methods to supply the flow and power

necessary to exceed pressure created by

dynamic loads .

Complicating the hydraulic-system design

are the many types of hydraulic pumps

available to create the needed flow . This

includes piston, vane and gear pumps .

Which one to use depends on the applica-

tion . Each pumping method has character-

istics that may make it a better choice for

some applications than others . Efficiency

and related heat generated play a big fac-

tor . For example, if an application always

needs full flow and pressure, a piston pump

may work just fine, but it will continue to

consume the same energy when the sys-

tem is at idle . I recommend creating your

hydraulic system work requirements and

then collaborating with your favorite hy-

draulic vendor to select the proper power

unit, as there are many options .



There are also many specialized and some-

times custom hydraulic fittings and mani-

folds, along with tubing and hoses that may

require special tools to assemble and build .

Whether flexible hose or high-pressure

tube, the hydraulic fluid conductors deliv-

ering flow and pressure to motion-causing

devices takes some planning and design . It’s

significantly different

than typical pneumat-

ic components .

The valves for start-

ing, stopping and

direction control are

much different, as

well . Given the non-

compressible nature of oil, servo-controlled

hydraulic valves provide more rigid and

stable position of cylinders than other com-

pressible methods .

With the correct hydraulic power unit

selected, consider the maintenance in-

volved . Hydraulic flow and pressure are

just some of the operational parameters

that are monitored today . Other diag-

nostic instrumentation can be added to

aid troubleshooting and future predictive

maintenance . This includes filter differen-

tial pressure, fluid level and temperature

sensors . Taking the time to add some

sensors and electronic controls can make

a more efficient,

precise and reliable

hydraulic system .

When hydraulics is

the best choice for

an application, take

the time to work

with the hydraulic

vendors and distributors . These hydraulic

power units are some of the low-hanging

fruit for cloud-based analytics, so add

sensors for data collection and monitor-

ing and get it connected to the plant net-

work . Proper hardware, design and moni-

toring will ensure a leak-free, efficient,

long-term solution .

Don’t let oil leaks from the past

sway your decision to use hydraulics .

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Get motors rolling and add feedbackKeep an ear out for electromagnetic interference and radio frequency interference

By Tom Stevic, contributing editor

Modern motors such as ac, dc and brushless dc servos are all different in con-

struction but have some performance characteristics . However, each design has

particular strengths and weaknesses . A dc motor typically has a bit more starting

torque than an ac motor, but brush-style dc motors may require maintenance to replace the

brushes . The brush action can also cause electrical electromagnetic (EM) and radio frequen-

cy (RF) noise . Having a good model of the mechanical requirements will make choosing the

correct motor torque, speed and power easier . There are many free motor-sizing tools avail-

able on the Internet to make the selection easier .

Both the National Electrical Manufacturers Association (NEMA) and the International Elec-

trotechnical Commission (IEC) have standard motor size specifications . Using a standard-

sized motor allows different manufacturers’ equipment to be used interchangeably . If a

motor must be changed from one brand to another, consider also changing the drive or

amplifier to the same brand, especially with servo motors . If technical issues arise when dif-

ferent motors and drives are employed, many manufacturers offer little assistance and tend

to blame each other instead of trying to solve the problem .

Manufacturers often offer many options when ordering a motor . Brakes, shaft seals, connec-

tor style, smooth shafts or keyways and connector styles are a few . Having many options

makes picking the perfect product for your application easier . A downside to the many





options is the availability of a replacement

part . Distributors and warehouses may not

keep one part of each possible combination

in stock . Choosing a motor that is normally

stocked, even if it has options that will not

be used, may better serve your customer .

One machine builder I have worked with

would list all of the possible motor combi-

nations that could be used directly on the

electrical prints .

Some motor manufacturers offer special or

custom designs . These should be utilized

only as a last resort in manufacturing equip-

ment . Be aware of the lead time required if

motor replacement becomes necessary at

some point . Plant managers are usually not

very understanding when machines are idle

waiting on some special part to be built .

In a closed-loop servo motion control sys-

tem, the motor’s actual position is com-

pared with its commanded position . Typical

feedback devices include resolvers, incre-

mental encoders, absolute encoders and

Hall effect sensors . Although not typically

used in an industrial system, analog ta-

chometers and rotary potentiometers may

also serve as feedback devices .

Resolvers are simple rotary transformers .

An analog excitation wave is supplied to

a single primary winding . Two secondary

windings are typically mechanically spaced

90° apart . As the resolver’s primary winding

is rotated, the secondary winding generates

sine and cosine waveforms that represent

the rotational angle of the primary . Resolv-

ers provide an absolute position whenever

they are under power . However, electro-

magnetic interference (EMI) and radio

frequency interference (RFI) may influence

the analog output signals . Proper shielding

is essential . Resolvers are rugged and can

operate in the harshest environments .

Incremental encoders produce one to three

pulsing signals . A single-phase encoder sup-

plies x number of square wave pulses per

rotation . A quadrature encoder outputs two

signals that are 90° apart . With this infor-

mation, the controller can determine rota-

tional direction . A third square wave pulse,

called the z phase, is output once every

revolution . If power is interrupted for the

encoder or the controller, a system using

an incremental encoder would need to be

“homed” before use .

An absolute encoder outputs a binary

count, depending on the angular position of

the encoder . Typical count values are 255

(8 bit), 1,023 (10 bit) and 4,095 (12 bit) . An

advantage of an absolute encoder is the

encoder supplies its rotational angle upon

power application . Mechanical and electri-

cal multi-turn options can provide direct

positional information to remove the need

to home a system . A considerable price dif-

ference once existed between incremental

and absolute encoders . This difference is

becoming less and less .



Feedback signals from an encoder may be

transmitted to the controller in several ways .

The oldest, and perhaps the simplest based

upon electronic component count, is a direct

wire connection between the motor-mount-

ed encoder and the system controller . A dis-

advantage of this approach is the low volt-

age susceptibility to EMI; and, if the encoder

is an absolute style, increasing the resolution

increases the signal wire count .

Manufacturers have developed proprietary

serial communication protocols as an im-

provement over the parallel method . Some

manufacturers have allowed their systems

to be open standard, free to be used by

anyone else . They include these three .

1 . Synchronous serial interface (SSI) was

developed in 1984 by Max Stegmann, now

Sick Stegmann (www .sick .com) . The SSI

interface is based upon RS-422 standards

and removed the need for multi-conduc-

tor cables and replaced them with two or

three twisted-pair communication cabling .

2 . Biss, developed by iC-Haus (www .ichaus .

de), included concepts from SSI and

Interbus . Multi-slave bidirectional commu-

nications using RS-485 uses one twisted

pair and, optionally, one set of power wire .

Additional registers in the encoder allow

motor information and additional sensor

readings, such as motor temperature, to

be retrieved from the encoder at will .

3 . A rather recent development by Sick is

Hiperface DSL . This open technology in-

corporates the motor supply wiring with

the position feedback signals in a single

cable . Additionally, it can provide motor

information such as temperature, me-

chanical revolutions, diode current, motor

specifications and serial numbers . Hiper-

face uses eight wires for communications .

Two for RS-485 communications, two

for power and four for 1-V peak-to-peak

sine/cosine .

According to an informal, nonscientific

poll of some maintenance personnel I’ve

worked with over the years, the single

most common source of failure in a servo

system is the motor connection cable . This

part should be the easiest to build . Some

of these failures may be a misapplication

of nonrobotic cables in a system where

the motor movement causes the cable to

flex . However, most maintenance people

have told me, “If the servo stops, change

the cable first .” I would suggest that, if you

have an option to buy higher quality cable

when the system is built, spend the extra

money . The people who keep your machine

running may never know, but they will not

curse you for it .

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Smart control and drive integration fills the billItaly’s Goglio wins Smart Machines category in Best Future Machine Awards

By Giancarlo Truglio, Goglio

At the inaugural Rockwell Automation Best Future Machine awards, announced at

interpack 2017 in Düsseldorf, Germany, Goglio (www .goglio .it) of Milan, Italy, won

top honors in the Smart Machines category with its GCap6 filling machine for alu-

minum capsules . The judges were impressed with the machine’s remote-access capabilities

and its use of Rockwell Automation’s Connected Enterprise technologies . Goglio’s smart

machine showcased technology-related safety, integration, information, real-time diagnos-

tic, operating efficiency and data tracking .

The awards were created to recognize and

reward the high levels of innovation in the

packaging industry . Additional categories

included Modular Machines, Sustainability,

Traceability & Product Safety and Ease of

Use . The Goglio filling machine rated well in

all categories (Figure 1) .

Italy’s Cama Group won the Ease of Use

category, as well as the overall Best Fu-

ture Machine Award for its IF318 Robotised

Monoblock Loading Unit, which incorporates



SMART AND GOOD-LOOKINGFigure 1: The Goglio GCap6 filling machine is ergo-nomic, noiseless, safe and modular, making it easy to install, update operate, maintain and clean.(Source: Goglio)



cabinet-free technology and ergonomics

and uses the iTrak intelligent track system

from Rockwell Automation .

YEARS OF BEING SMARTGoglio is synonymous with quality, com-

petence and commitment in packaging .

The Italian company has gone through the

entire history of packaging . In 1850, the first

company of the group, specializing in paper

bags, was founded; in 1909, the first mecha-

nized factory was born; in the 1960s, the

Fres-Co System was designed to integrate

flexible packages with packaging machines

and technical service; in the ’70s, new facili-

ties were built in Daverio, Italy, to manufac-

ture flexible packaging material, in Milan,

Italy, to manufacture plastic for valves and in

Zeccone, Italy, to build machines . The Go-

glio Group invented the one-way degassing

valve, still an important component in coffee

applications, as well as in other packaging

processes . After a period of expansion in the

1980s, Fres-Co System International in the

Netherlands, Fres-Co System Espana and

Fres-Co System USA were opened . In the

’90s, the Goglio Group consolidated its pres-

ence in Europe with Goglio North Europe

located in the Netherlands . New branches

in the United States, Poland, Italy, Japan,

France, China and Brazil were opened at the

beginning of the 21st century and in 2016 the

company entered the capsules market .

Today, Goglio designs, builds and delivers

complete solutions for the coffee industry .

This includes packaging film material, de-

gassing valves, packaging machines, cap-

sules and capsule-filling machines, as well

as 24/7 technical assistance and service .

SMART COFFEEA good example of Goglio’s deep knowl-

edge in coffee is the GCap6, a filling ma-

chine for aluminum capsules . In addition to

coffee, this automatic line for capsule filling

and packing is also suitable for use with tea,

infusion and instant drinks (Figure 2) .

The GCap6 filling machine includes several

modules: a loading system for stacked cap-

sules, a twin-auger filling system, a check-

weigher, a tamping and cleaning device, a

top lid cut and seal group, an optical cam-

era control and an exit pick-and-place . The

capsules are fed to the conveyor through a

singulating device and a carousel . A pick-

and-place system takes six capsules at a

COFFEE, PLEASEFigure 2: The Goglio’s machine fills aluminum coffee capsules and is suitable for filling tea, infusion and instant-drink capsules as well.(Source: Goglio)



time from the carousel and releases them

on the indexing conveyor that transports

them to the different stations .

In a typical application, the machine fills

capsules with ground coffee, which is fed

directly from the grinder and pan-feeder .

The spinning blender above the twin augers

keeps the density of the coffee constant .

The weight of each capsule is then checked,

and feedback is sent to the augers . The in-

dexing conveyor moves the capsules under

the tamping device that presses the coffee

with a vertical motion and cleans the up-

per flange to remove any coffee that could

get stuck between it and the top lid with a

rotating motion .

The capsules are then brought to the cut and

seal group where another vertical movement

cuts a circle of aluminum and places it on the

upper flange of the capsules in the conveyor

(Figure 3) . A second part of the group then

seals them . A 180° rotating pick-and-place

device grabs the capsules that are lifted

from the conveyor by a pneumatic cylinder

and placed on a tilt device . The capsules are

then released on the exit conveyor with the

larger flange facing the belt .

SMART CONTROLGoglio designed the automation system of

the GCap6 selecting several Rockwell Au-

tomation solutions . Rockwell is one of our

main suppliers and works with us on a daily

basis in the development of new products .

It is one of the most important brands and

provides a wide-assistance network world-

wide, together with great technical support

to the machine builders .

The control system on the GCap6 consists

of an Allen-Bradley ControlLogix controller,

an EtherNet/IP network and several Kinetix

5700 EtherNet/IP servo drives (Figure 4) .

All of the devices are connected through

EtherNet/IP while a Stratix 2000 unman-

aged switch allows easy connections within

the control network .

WEB AND MATERIAL HANDLINGFigure 3: Over a dozen axes of servo motion controls the various modules on the machine, such as this cut-and-seal group.(Source: Goglio)



The Kinetix drives control

over a dozen axes including

the rotating table for inser-

tion of stacked capsules,

the pick-and-place system

inserting the capsules in the

conveyor and the indexing

movement of it, the augers,

the checkweigher lifting

movement, the tamping

device, the cut-and-seal de-

vice, the exit pick-and-place

and the reel unwinding .

Additional Kinetix ac servo

motors are used for the pan

feeder blender, the twin

auger blender, the cleaning

brush, the tamping heads

and the exit conveyor .

Coordination of each mo-

tor is essential on the filling

machine . The use of servo

motors allows each function

to be fully synchronized and

coordinated in an electronic

cam and enables noiseless

operation . All motorized

functions are linked to an

electronic cam with a virtual

axis within the machine,

which runs from 0° to

360° during each machine

cycle . Using this solution,

the optimal synchroniza-

tion is maintained, with

automation compensation

as machine speed varies,

improving overall machine

performance .

Servo motion provides an

automatic speed adaptation

among the different func-

tions and guarantees con-

stant timing of each feature,

whether a simple or com-

plex motion function . One

of the most critical motion-

control functions is the top-

lid piercing and sealing sta-

tion because it is a one-step

process in a single station .

Therefore, the requirements

of time and synchronization

are very demanding . Any

errors can lead to poor cycle

time and wasted material .

A motorized unwinder

enables use of up to 500

mm reels on the machine

instead of the standard 300

mm, which reduces the time

and manpower needed to

change reels . In addition,

the machine’s simplicity and

ergonomic design provide

easy operator access for

maintenance .

MORE AXES, LESS SPACEFigure 4: Servo drives include dual-axis modules with a single-cable connection between each axis and servo, saving space and integration time. (Source: Goglio)



SMART INTEGRATIONThanks to the Rockwell Automation single-

cable motion system, Goglio can minimize

wiring to the Kinetix 5700 servo drives .

These drives also use dual-axis modules to

help reduce the space needed in the electri-

cal cabinets . Even in the complex filling ap-

plication, this is a simple motion system to

integrate as its use reduces the amount of

cable installed for each motor by 50% . The

dual-axis modules are almost the same size

as a typical single-axis drive, reducing the

panel space needed by about 50%, as well .

Furthermore, the user-friendly software

programming environment made machine

development easier . The machine is de-

signed to be configurable to specific ap-

plication needs, using the PanelView Plus

7 operator interface, while still working in

complete synchronicity . Our programmers

developed and optimized this software to

include different process combinations, and

each function is separately accessible for

instant customization and machine opera-

tion (Figure 5) .

The machine is remotely accessible via

Ethernet and can communicate with both

a customer’s MES and/or with the Goglio

developed cloud platform . Production data,

including recipes, batch number and quan-

tity to be produced, can be remotely sent

to the machine . The design allows a cus-

tomer to collect all analog and digital data

from the machine and then use that data to

implement analytic and predictive mainte-

nance applications .

HOW DO YOU LIKE YOUR COFFEE?Figure 5: An operator interface enables quick configuration and control of machine operation.(Source: Goglio)



A separate PC allows operators to manage

data and information to produce alarm and

production reports and display any needed

manuals, catalogues and diagrams . The PC

also includes the tools needed to manage

maintenance and camera visualization .

This Goglio smart filler machine achieved

other advantages including reduced training

times, improved machine flexibility, better

troubleshooting of operational problems and

easier testing and validation; it also helped

to minimize installation and startup times .

Not only does this smart machine pro-

vide high performance and 94-95% overall

equipment efficiency (OEE), it looks good,

as well . The machine offers very good seal-

ing, cutting and dosing accuracy in addition

to precise defect checks . A combination of

the machine’s applied design, feedback to

load cells, photo eyes and cameras help to

detect the presence and quality of capsule

components . In addition, the servo tech-

nology allows the machine to efficiently

achieve high availability, speed and quality .

Giancarlo Truglio is the research and

development manager and machine

division technical department vice

director at Goglio in Zeccone, Italy . Contact him at

giancarlo .truglio@goglio .it .

©2

01

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Inc.

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