energy saving with inverter drive

7/30/2019 Energy Saving With Inverter Drive

1/12

ENERGY SAVING WITH INVERTER DRIVE

Introduce Inverter or AC driveDrive is device that convert frequency and voltage

Configuration of Inverter Main CircuitThe rectifier circuit sectionis composed of 6 pairs of diodes, and the smoothing section (or DC bus)uses

electrolytic capacitors. The inverter conversionsection is composed of 6 pairs of transistors (IGBTs are often used for

these transistors).

Principle of AC Voltage Generation

S1 through S6 are IGBTs that switch according to the switching pattern shown below. This switching

generates 3-phase voltage between U and V, V and W, and W and U. Current flows between Section a and Section b in

the figure below.

Actual Output Voltage Waveform

The waveform created in the switching patterns on the previous page is a square wave. A sine wave,

however, is more preferable for accurate motor control. In the diagram below, IGBT switching creates the waveform, a

technique called, pulse width modulation (PWM). PWM is capable of creating a waveform very similar to a sine wave.

Example of Actual Inverter Main Circuit and Control Circuit

In addition to the main circuit described in the previous slides, inverters also have various I/O terminals to

send commands and connect various devices to the inverter.

The next slide shows input terminals on the left side of the drive. The input terminals are made up of contact

relays that switch on and off, instructing the drive to execute a certain command (such as Reverse run, Stop, and so

on). In addition to contact relays, analog inputs and a pulse train input are also available to control the speed. Some

inverter drives also come with inputs for serial communications, allowing the drive to be controlled by a PLC or connect

to network.

The right side of the diagram on the following slide shows the output terminals for other devices that are

activated by drive output. Various functions can be set up to these outputs terminals, so that the user can check the

output frequency and output current the drive is sending to the motor. Contact relays are also found among the output

terminals that can be set up to switch when a fault occurs, when the speed reference and actual motor speed match, or

a multitude of other functions. Drives also come with an output terminal that sends a series of pulses to control thespeed of another drives.

The digital operator keypad used to program the drive can also be used to display information regarding the

operating status (output current, output frequency).

Concept of Energy Saving

APPLICATION HOW DRIVES SAVE ENERGY

Fans, blowers, Flow rate and air flow quantityReplacing with motors of better efficiency


2/12

pumps

constant Collecting energy for excess facility capability (inverter application)

Flow rate and air flowquantity variable

Recovering throttling loss of valves or dampers (inverter application)

Extruders,

conveyors

Speed variableUsing an inverter drive makes an overall more efficient application(Eddy-current coupling drive Inverter drive)

Speed constant Replacing with motors of better efficiency

Lifting machines such as cranesInverter power supply regenerative function collects theregenerative energy at lowering.

Unwinders Re-use regenerative energy created by the unwinder.

Descaling pumps Stores up energy for starting torque

Fans: Energy Saving with Variable Speed Control

Fan shaft power

Fan shaft power P is in proportional to the product of the air flow quantity q and pressure h.

q: Air flow quantity (m3/minute)

h: Pressure (kPa)

: Fan efficiency

Partial Load: Energy Saving

At partial load means operation at less than full load (rated air flow quantity). With a commercial powersupply, at partial load indicates the status at which operation is performed when the air flow quantity is reduced by

damper.There are mainly two types of dampers: a suction damper provided at the fan inlet, and a discharge damper

provided at the fan outlet.

Characteristics of Fan Air Flow Quantity and Pressure, and Principle of Energy Saving

H stands for the fan characteristic and R for air flow resistance at rated number of revolutions N. A, the

intersection point of H and R, is the rated operation point of the fan. At point A, the air flow quantity and pressure is

1.0 of the rating. When the damper is throttled in order to reduce the air flow quantity to 50%, the curve of air flow

resistance changes from R to R0.5. The power at that point is expressed with the area of HoQ0.5AdHd. Becausecontrolling the speed reduces airflow by 50%, if we assume the change in speed from N to be N0.5, and the change in

fan characteristics from H to be H0.5, then the amount of energy saved is found be calculating the area HoQ 0.5AiHi .

Formula of shaft power P:Unit of Q, H: p.u. (per unit)

(kW)HQ60

QH=P oo

f


3/12

Fan characteristic H is approximated at the following formula: = 1.03N2 +0.56NQ - 0.59Q2, Air flow resistance R is approximated at the following formula: R =Q2 , Rated air volume Qo: 1000 m

3/minutes, Rated pressure: 5kPa, Fan efficiency atrated air flow quantity: 0.7, Fan efficiency at 50% air flow quantity = 0.54

Inverter Energy-saving Effect

When applied to a fan with air flow quantity 50%

Power at damper control [Pd] H = 1.03N2 + 0.56NQ - 0.59Q2

Air flow pressure at air flow quantity 50% is: Hd = 1.03 x 1 + 0.56 x 1 x 0.5 -

0.59 x 0.52 = 1.16

Power:

m = 0.9: Motor efficiency

Power at inverter control [Pi]R=Q2

Air flow pressure at air flow quantity 50% is: Hi=0.52=0.25

Power:

i = 0.95: Inverter efficiency

Power saving amount [Ps]Ps = PD Pi = 99.5 - 17.4 = 82.1 k

Assuming that power unit price is 15 yen/kWh and the fan runs continuously for

one year (8,000 per year), then cost savings can be expressed as

82.1 kW x 15 yen x 8000 hrs = 9,852,000 yen per year!

Characteristic of Power Consumption for Air Flow QuantityWhen using an inverter, power consumption is either greater or equivalent to the inverter loss at 100% air

flow quantity than when using damper control. However, as soon as the air flow quantity is reduced, the power

consumption is rapidly reduced at inverter control.

Energy-saving Effect at Full Load

When installing a fan, the fan capacity written in the fan specifications usually includes allowances for

performance deterioration due to aging. In this case, the air flow quantity is set to the required value by installing the

fixed throttle for the air tunnel. By removing this fixed throttle and setting so as to obtain required air flow quantity by

using rotational speed control, the power indicated in the shaded section can be saved as well.

Shaft Power of PumpPump shaft power P is in proportion to the product of flow rate and pump head.

q : Flow rate (m3/minute)

h : Pump head (m)

p: Pump efficiency

Actual Pump Head

99.5kW=510000.90.5460

1.160.5=HQ

60

QH=P oo

mf

D

17.4kW=510000.950.90.760

0.250.5

=HQ60

Q

=P ooimf

i


4/12

In pump applications, the value for the actual pump head is normally provided. Actual pump head is the

difference of height between the water level of the discharge tank and the suction tank as shown in Fig. (a). In

fan applications, the air flow pressure is 0 when the air flow quantity is 0. However, in pump applications, the pressure

that is always applied to the actual pump head is added to the pump even if the flow rate is 0.

Since actual pump head becomes 0 for a circulation pump as shown in Fig. (b), a circulation pump can be regarded in

the same way as a fan.

Characteristics of Pump Flow Rate and Pump HeadCalculating Inverter Energy-savingWhen applied to pump at flow rate 50%

Power at valve control [P B] H=1.25N20.25Q2Pump head at flow rate 50%: HB = 1.25 x 1

2 - 0.25 x 0.52 = 1.188

Power:

m = 0.9: Motor efficiency

Power at inverter control [P i ] R =0.7+0.1Q2Pump head at flow rate 50%:= 0.7 + 0.1 x 0.5

2 = 0.725

Power:

= 0.95: Inverter efficiency

Saved power [Ps ] Ps = PB Pi = 115.5 - 54.7 = 60.8 kW

Assuming that power unit price is 15 yen/kWh and the pump runs continuously for one year (8,000 per year), then cost

savings can be expressed as

60.8 kW x 15 yen x 8000 hrs = 7,296,000 yen can be saved.Characteristics of Flow Rate and Efficiency

The following shows the characteristics of the pump efficiency for the flow rate. The 100% speed

characteristics show the efficiency characteristics when using valve control. It can be seen that the efficiency decreases

due to reduction of the flow rate. Efficiency decrease when the flow rate is reduced by rotational speed control at the

peak point of the pump efficiency characteristics at each speed. We can see that there is no efficiency reduction up to

50% speed. Although the efficiency is reduced to 0.88 at 20% speed, the reduction is very slight compared to the

efficiency reduction 0.35 in case of valve control. The relation between the fan air quantity and efficiency is almost the

same what we see for pumps.

Relation between Flow Rate and Rotational SpeedPump characteristic H and piping resistance R0 are calculated as follows in the example shown on the previous page:

H = 1.25N2 - 0.25Q2 , R= 0.7 + 0.1Q2

By replacing 1.25 with a , 0.25 with b , 0.7 with ha and 0.1 with c , the above formula can be expressed as follows:H = aN2 - bQ2, R0 = ha + cQ2

Since the pump operating point is where H and R0 intersect, H equals R0. In other words,

aN2-bQ2=ha+cQ2Therefore, rotational speed N is:

Accordingly, the flow rate is not proportion to the rotational speed.

115.5kW=25240.90.566.12

1.1880.5=HQ

6.12

QH=P

oo

mp

B

54.7kW=25240.950.90.766.12

0.7250.5=HQ

6.12

QH=P

oo

imp

i

a

c)Q+(b+h=N

2

a


5/12

Then formula (1) becomes as follows when actual pump head is 0:

Only when the actual pump head is 0, the rotational speed is in proportion to the flow rate.Since there is no actual pump head in case of fans, it is always in proportion to the flow rate.

Energy Saving by Replacing Variable Speed Drive SystemOther AC variable systems other than inverter drive include VS motors (motor with eddy-current coupling) as

well as the winding motor secondary resistance control method. The figure below shows the configuration of a VS

motor. The motor to be driven is always turning at a constant speed. Eddy-current coupling is composed of the drum

connected directly to the motor and the magnetic coil connected directly to the load side. By applying the DC current

to the magnetic coil, eddy current is generated in the drum. Torque is generated by this eddy current and by the

excited current flowing in the coil. Load shaft connected directly to the coil rotates at the slip almost in proportion to

the torque. Since the slip can be adjusted by controlling the current flowing in the coil, the load shaft speed can be

adjusted, too.

Principle of Speed ControlThe following graph shows the characteristics of rotational speed and torque of an eddy-current coupling. In

the graph below, ais the torque characteristics when excitation current is large. The operating point is the point of

intersection Pa with load torque T . Thus the rotational speed is Na. When the excited current is reduced and thetorque characteristic becomes b, the point of intersection with T is Pb, and the rotational speed is reduced to Nb. In

this way, adjusting excitation current can control the speed of the load shaft.

Mechanical SpecificationsTo calculate torque T L relative to output P and rotational speed N,

Motor rated speed 1750min-1

VS motor output shaft rated speed 1500min-1

Motor input power at 1750min-1 37kW

Motor efficiency 91%

Load torque TL at 37kW input and 1750min-1 is calculated based on the above specifications:

Constant Torque LoadTo calculate power P relative to torque TL and number of revolutions N,

(1) Calculating energy saving when operating with constant torqueWith a VS motor or secondary resistance control, reducing the speed reduces the motor shaft output in proportion to

the speed. However, because this reduction in output is essentially a loss , the motor input power is almost thesame.

Using an inverter to adjust the speed can eliminate this loss.

Output power when using a VS motor37 kW. This is because the motor input power does not change even if the speed is reduced.

Output power when using an inverter driveAssuming that the motor efficiency is 87% and inverter efficiency is 95% at 750min-1,

inverter input power will be:

Qa

c+b=N

(Nm)1000N2

60P=TL

Nm183.5=100017502

370.9160=TL

(kW)1060

NT2=P

-3L

kW17.4=100.950.8760

750183.52 3-


6/12

Amount of energy saving37 kW17.4 kW19.6 kW

If the pump operates for 6000 hours a year with power unit price 15 yen/kWh, then:

19.6 kW 15 yen 6000 hrs1,764,000 yen saved!(2) Calculating energy saving at square reduction torque loadTorque is reduced in proportion to the square of the speed.

Power when VS motor used183.5 0.25 = 45.9 Nm since torque becomes 25% of that at rated speed.

Calculate the motor input as follows. Assume that the motor efficiency is 83% at 1750min-1 with a

load ratio of 25%.

Power when inverter usedInverter input power is calculated as follows assuming that the motor efficiency is 82% and the

inverter efficiency is 95% at 750min-1 and load ratio 25%.

Energy saving amount10.1 kW4.73 kW5.37 kW

If the pump operates for 6000 hours a year with power unit price of 15 yen/kWh, then:

5.37 kW 15 yen 6000 hrs = 483,300 yen saved!Energy Saving by Power Regeneration of Mechanical EnergyHow a load creates regeneration

When a crane is lowering a load or when winder is unwinding a load, the motor acts like a generator, creating

energy as the load pulls against the rotation of the motor. This is considered the regenerative status.

Regenerative Energy Processing by Braking ResistorRegenerative energy flows into the inverter from the motor when the motor enters into regenerative status.

This regenerative energy increases the voltage in the DC bus, and can trigger the overvoltage protection function (thus

causing the drive to stop). In order to prevent this, a braking unit and a braking resistor are added in a general-

purpose inverter drives to absorb regenerative energy and dissipate it as heat.

Using Regenerative Energy in an Inverter DriveTypical Calculation for Energy Saving

The following example shows an inverter with a regenerative function used to operate a crane application.

Crane specifications

Rated load :10tRated hoisting speed :22 m/min

Applicable motor capacity :45 kW

Motor speed :1150 min-1

Machine efficiency:87%

Using the specifications listed above, rated motor torque T is calculated as follows:

kW10.1=100.8360

175045.92 3-

kW4.73=100.930.8260

75045.92 3-

NmT 3741150

45

2

60=

=


7/12

Operation Pattern

Calculating Energy SavingRequired power:

Load torque:

Load inertia:

Assuming that the motor inertia is 0.49 kgm and machine inertia is 0.75 kgm, the total inertia is: 0.49 + 0.75 +

0.0927 = 1.333 kgmAcceleration torque:

Acceleration torque when lowering :91.70.87228.740.7

Constant speed torque when lowering :91.70.87269.4

Deceleration torque when lowering :69.428.798.1

Regenerative power is calculated as follows when the motor efficiency is 90% and inverter efficiency is 95%:

P = 450.407/21.5 + 0.69415 + 0.981/21.5)/760.950.9 = 5.8 kW

If the crane operates for 3600 hours with power unit price of 15 yen/kWh, then cost savings becomes:

5.8 kW 15 yen 3600 hrs = 313,200 yen saved!

Energy Saving by Motor Operation with High EfficiencyInverter drives control frequency and voltage. This explains how inverter drives are used to achieve higherefficiency from the motor. The graph below shows the motor slip-torque and efficiency characteristics. Imagine a case

where the load of the machine is being driven at rated load T L1 is reduced to TL2. When the load is TL1, the motor is

running at slip S1 determined by P1 (the intersection of motor torque characteristics TM1 and load torque TL1). The

efficiency at that point is 90%. When the load is reduced to T L2, slip S2 is determined by point P2 (the intersection of

TM1 and TL2).

The efficiency is reduced to 72%, lower than the efficiency at rated load. However, the efficiency becomes

90% since the slip is changed again from S2 to S1 when voltage is reduced so that the torque characteristics will be

TM2. In this way, by controlling the voltage according to the load, the motor can always be driven with greater

efficiency. Yaskawa calls this the Energy Saving Control function. We offer this function in most of our drives.

Energy Saving Control Block DiagramA block diagram illustrating Energy Saving control appears below. During acceleration, switch SW closes on

side 1 to output voltage as determined by the standard V/f pattern. Once acceleration is complete, SW then switches

over to side 2, and outputs voltage at the maximum efficiency as calculated by the load conditions and the frequency at

that point.

Typical Calculation of Energy SavingEnergy Saving in centrifugal separator

Although a great deal of power is required to accelerate the load in a centrifugal separator due to the large

inertia, it becomes relatively light when operating at a constant speed. The figure on the left shows the operation

cycle. Even if the Energy Saving control is available, it is not active during acceleration (i.e., the power required to use

41.3kW=0.876.12

2210=

6.12

VW=PL

.7%)342.9Nm(91=1011502

41.360=10

2

P60=T 33LL

0.0927kgm1150

22

4

1010=

N

V

4

W=J

32

L =

2

Nm(28.7%)107.0=1.560

11501.3332=60t

NJ2=T


8/12

Energy Saving is equal to that when Energy Saving control is disabled). We should therefore compare the power

required with a light load after acceleration.

Specifications of centrifugal separatorApplicable motor : 400 V 75 kW 4P Yearly operation time: 8000 hours

Inverter efficiency : 95% Power unit price: 15 yen/kWh

Calculating Energy Saving Inverter operation without energy-saving control

Motor output power at constant speed:

Inverter input power:

Average power in one cycle: 1 = 10.41800/2340 =8.00 kW Energy-saving control inverter operationMotor output power at constant speed:Inverter input power:Average power in one cycle: 2 = 9.181800/2340 =7.06

According to the above calculations:

Electrical charge of8.00 - 7.06800015 = 112,800 yen can be saved.New Motor and Inverter TechnologiesNew motor technology

Motor loss must be reduced in order to improve the motor efficiency. There are 4 types of motor loss:

stator copper loss, rotor copper loss, iron loss, and mechanical loss. Reducing these four types of loss

improves motor efficiency.

Motors called high-efficiency motors or power-saving motors are designed to minimize loss types and

. To reduce stator copper loss (), increase the size of copper wire used in the motor windings. For , iron core

material is upgraded to minimize the loss. Unlike induction motors, synchronous motors use permanent magnets forthe rotors, and consequently have hardly any rotor copper loss. This makes synchronous motors capable of even

greater efficiency.

Cross Section of a MotorFor greater efficiency Yaskawa has designed synchronous motors using permanent magnets with the product

name Super Energy Saving Motor, and super econo motor. The figures below illustrate how each motor is built.

Fig. (a) is an induction motor where the magnetic flux is generated in the stator winding. Fig. (b) is a Super Energy

Saving Motor where the magnetic flux is generated by permanent magnet implanted in the rotor. Fig. (c) is a super

econo motor which has a permanent magnet implanted in the rotor of an induction motor. This motor can be driven by

standard line power while the Super Energy Saving Motor cannot be driven by line power. At start, it generates torque

as an induction motor using current flowing in the rotor conductor, then operates as a synchronous motor when the

speed is close to the synchronous speed.

Principle of Super Energy Saving Motor Rotation

7.5kW=1060

1790402=P 310

10.4kW=0.950.76

7.5=P1i

7.5kW=1060

1790402=P 320

9.18kW=0.950.86

7.5=P2i

7.5kW=1060

1790402=P 320

9.18kW=0.950.86

7.5=P2i


9/12

New Inverter TechnologyThe diagram below illustrates five steps that can be taken to improve motor control and inverter drive

performance: Reducing the loss generated in the inverter unit; and concern circuitry and the control method

used for high-efficiency performance; covers improvements to drives power supply side; involves a new

approach to power conversion.

Reducing Inverter Component LossOne way to improve inverter efficiency is to reduce loss from various components. The circle graphs below

show the amount of loss generated from each component in the drive. About 10 years ago, the loss generated from

IGBT (Insulated Gate Bipolar Transistor) switching in the main circuit exceeded 60% of all loss. Recent improvements

in switching technology have now minimized loss from IGBTs down to 40%.

Improving the switching characteristics of the IGBT device has reduced the power loss to the half of what it

was 10 years ago. In addition to reducing power consumption for the control power supply and control circuit, inverter

efficiency is 9o% better than in the past.

Improvements with PWM ControlThe high carrier frequency used in PWM (pulse width modulation) increases the amount of IGBT switching

loss. Yaskawa has created a 2-phase modulation method to minimize this switching loss.

As shown below, the 2-phase modulation method stops switching when current is large. This way, one of the 3 phases

is always in the stopped status. Using this 2-phase PWM control method can reduce the switching loss by approx. 30%.

Employing 2-phase modulation can reduce IBGT switching loss by approximately 30%.

Improving the Output Voltage WaveformAlthough high carrier PWM control makes the output current waveform very close to sinusoidal, the actual

voltage waveform created is still a group of square waves. The surge voltage generated at rising and falling edges of

this square waves causes trouble. A surge suppression filter is normally attached between the inverter and the motor

in order to prevent the motor insulation from being damaged by surge voltage. This filter is called RLC filter, and is is

composed of a resistor, reactor, and a capacitor.

A large filter is not needed if the inverter and motor are close together. If they are far apart, however, a large

capacity filter is needed. For example, with the motor capacity of 75 kW, the filter consumed power is 0.3 kW, 1.4 kW

and 12.6 kW when the wiring length is 30 m, 100 m and 300 m, respectively. As the distance gets longer, the required

capacity is sharply increased. Additionally, the size of the filter also becomes larger, it will be necessary to examine

where to install. To omit this filter, 3-level control inverters have been devised. Using these inverters can solve the

problem of. Furthermore, this control method can reduce the remaining 3 failures (, and) at the same time.

Common Problems Motor insulation damaged by surge voltage

Peripheral devices malfunctioning due to noise generated by the inverter

Earth leakage breaker malfunctioning due to leakage current

Motor bearings corroded by shaft current

What Is 3-Level Control?Principle of 3-Level Control Method

In conventional 2-level control, 2 transistors are used for each phase, making a total of 6 transistors for 3

phases to switch DC bus bar voltage VPN. Phase voltage turns ON and OFF depending on the size of VPN, and changes

according to it. In the 3-level control, 4 transistors are used per phase, for a total of 12 transistors for 3 phases. The

illustrations below shows how transistors switching works during one phase. In this figure, voltage P appears in phase

U when transistors A and B turn ON. Then O appears in phase U through diodes E and F when transistors B and C turn

ON. N appears when transistors C and D turn ON. It means that phase U can take three states: P, N, and O. This is

how 3-level control was named.


10/12

While voltage fluctuates between P and N in 2-level control, it fluctuates between P & O, and between O & N

in 3-level control. Therefore, phase voltage turns ON and OFF depending on the size of V PN/2, which is half of VPN during

2-level control. This creates an output waveform very close to a perfect sine wave. Surge voltage is cut in half when

voltage fluctuation becomes half, which means that noise and leakage current is also cut in half, resulting in reduction

of shaft current.

Comparison of Surge Voltage Waveform in 3-level Control MethodThe following figures show the output voltage waveforms of 400 V class inverter 2-level control and 3-level

control, respectively. In the 2-level control method, the peak value of the waveform is almost 1200 V, while it is limited

to 770 V in the 3-level control method. Since this value is lower than the insulation voltage of the 400 V class motor,

the existing motors can be driven by an inverter without using surge suppression filters.

Comparison of Radiation Noise in 3-level Control MethodThese graphs show noise levels. In the frequency bandwidth between 30 MHz and 300 MHz, the noise level is

limited to 20 dB at the maximum. This reduces the effects on surrounding peripheral devices caused by noise.

Comparison of Leakage Current in 3-level Control MethodThe graphs below compare leakage current in 2-level and 3-level control. Leakage current in the 3-level

control method is almost the half of that in the 2-level control method. Less leakage current means fewer faults with

the leakage breaker.

No Surge Suppression Filter Needed Because of Surge Reduction3-level control contributes to energy saving because there is no need for a surge suppression filter that would

otherwise consume power.

Consumed power WRof the resistor is calculated as follows:

WR= CfE2fi2

Cf: Capacitor size is determined by cable type or wiring length

E: DC bus bar voltage (600 V at 440 Vac input)

fi: Inverter carrier frequency2: Multiplied by 2 for charging and discharging of capacitor

Power Consumption of Surge Suppression Filter Energy saved because no filter is used

Improvement of Inverter Input Power FactorPower factor is approx. 0.65 when the inverter is connected directly to the power supply. However, it can be

increased to approx. 0.9 by connecting a DC reactor, and to up to approx. 0.95 with a 12-pulse rectifier.

Since improving the power factor decreases the input current needed, this in turn reduces the wiring loss,

therefore saving more energy for the entire system.

New Power Conversion Unit (Matrix Converter)Just to review, an inverter drive is used to convert line power to supply to some desired frequency and

voltage. It changes AC into DC in the rectifier circuit, then adjusts the voltage and frequency to the desired level.

Because a voltage ripple is created when converting AC into DC, a smoothing capacitor is needed between the inverter

and the power supply to even out this ripple. These capacitors take up space, making it difficult to design compact


11/12

inverter drives and also limiting the lifespan of the unit. A new design called the matrix converter offers a new

environmentally friendly approach to power conversion.

Features of eco-friendly matrix converters No capacitors in the main circuit: Smaller size, longer life

Free from power supply harmonics: Input current a near-perfect sine wave (distortion ratio: 5%) Power supply regenerative function: No braking resistor is needed, which contributes to space and energy

saving.

High conversion efficiency: Greater energy saving.

Matrix Converter and Inverter Main Circuit ConfigurationThe diagrams below compare the designs of a matrix converter main circuit and the inverter main circuit. The

matrix converter has a simple configuration. It is composed of 9 bi-directional switching elements, and does not have

the converter and DC bus sections which are needed for inverters. However, the controlling procedure is complicated

and needs high-speed calculation and two-directional switching elements. Since the two-directional element is

composed of 2 transistors in the reverse parallel, the actual number of transistors is 18.

Comparison of I/O WaveformI/O waveforms for an inverter drive and the matrix converter appear below.

There is a fair amount of distortion generated in the input current for an inverter drive, while matrix converter has a

near-perfect sine wave. Since the distortion ratio for the matrix is 5% or less, there is no need take extra steps to

prevent harmonic distortion (otherwise necessary in an inverter drive).

Power Supply Regeneration: Matrix Converters vs. Inverter DrivesMatrix converters dont need capacitors in the main circuit, so they can be built much smaller Space saving

Simple main circuit configuration without excessive loss High efficiency

Total 6 cables of main circuit wiring (3 at power supply side and 3 for motor side) Reduction of wiring and labor

Type Matrix converterPower supply regenerative PWMconverter + inverter

Inverter with regenerativefunction

Drive main circuitconfiguration

Input current waveform Similar to sinusoidalwave

Similar to sinusoidal wave Distorted wave

Smoothing capacitorNot needed(therefore longerlifespan)

Necessary Necessary

100% load continuousoperation at low speed

Possible Current reduction needed Current reduction needed

Mounting direction (m2) 0.201 0.364 0.252


12/12

Loss (W) 930 2200 1400

Number of main circuit wiringcables

6 20 6

Weight (kg) 45 118 59

BY: Marketing Suport YaskawaPT.INDOSERAKO SEJAHTERA

energy saving with inverter drive

Documents