nema iec and pilot device presentation

7/28/2019 NEMA IEC and Pilot Device Presentation

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Motor Controls

EETE 2 Technical Elective 2



OUTLINE

• Symbols: NEMA vs IEC

• Pilot Devices

•

Wiring vs Schematic Diagrams• Overcurrent vs Overload Protection

• Low Voltage Release vs Low Voltage

Protection



SYMBOLS



Symbols

•

Motor control language consists of symbols toform a circuit diagram.

• Contactors and motor starters are ratedaccording to size and type of load they are

designed to handle.• The National Electrical Manufacturers Association

(NEMA) and the International ElectrotechnicalCommission (IEC) are two organizations that rate

contactors and motor starters.

• Each organization has its own set of symbols.



NEMA

•

NEMA Contactors and Starters are designed instandardized sizes from 00 to 9.

• Each of these sizes has a defined current, and

a resultant voltage and frequency dependent

horsepower rating.

• No matter who manufactures the device, the

current and horsepower rating will be

identical for a given size.



NEMA

•

If a standard motor is being used, once itshorsepower rating is selected, the Contactor

or Starter horsepower rating is simply

matched to that of the motor.

• The nameplate of the Contactor or Starter is

labeled with the NEMA size, the various

horsepower and voltage ratings assigned to

the size, and its continuous current capabilityat which the NEMA Standard temperature rise

will not be exceeded.



NEMA• NEMA motor-control devices have generally become

known for their very rugged, heavy-duty construction.• Because of their rugged design, NEMA devices are

physically larger than IEC devices.



IEC

•

IEC Contactors and Starters are not designedto a standardized size.

• Instead a manufacturer certifies that he/she

has designed the device to meet a number of defined applications referred to as Utilization

Categories.



IEC

•

To properly match the IEC Contactor or Starterto the application requirements, the user

must know both the application requirements

and the capability of the Contactor or Starter

being selected.

• If the Contactor or Starter will not provide a

reasonable operational life in the application,

a larger device would need to be selected.



IEC• Not all applications require a heavy-duty industrial

starter.• In applications where space is more limited and the

duty cycle is not severe, IEC devices represent a cost-effective solution.



NEMA and IEC

Ratings Comparison

• NEMA Contactors and Starters can beapplied to AC-3 applications.

• They may also be applied at their normalstandardized ratings to AC-4 applicationswhere there will be no more than fiveopenings per minute and no more than 10openings during a 10-minute period.

• Beyond this level, NEMA provides a plugreversing and jogging duty table withmodified ratings for improved operating life.

• Many IEC devices also have a NEMA rating.



Additional Comparisons



Other Organizations

• There are several other organizations that havedeveloped standards and tests for electricalequipment.

•For example, contactors are tested byUnderwriters Laboratory (UL) using testprocedure UL508, which specifies a maximumhorsepower rating for which a contactor can be

used.• Deutsches Institut für Normung (DIN), the

German national standards organization

http://en.wikipedia.org/wiki/Deutsches_Institut_f%C3%BCr_Normung





NEMA vs IEC

• The following comparison of circuit symbols is

based upon the following

international/national specifications:

• IEC 60617 graphic symbol database

(DIN EN 60617-2 to DIN EN 60617-12)

• NEMA ICS 19-2002, ANSI Y32.2/

IEEE 315/315 A, CSA Z99



NEMA vs IEC



NEMA and IEC Terminal Markings

NEMA d IEC C t ll M ki



NEMA and IEC Controller Markings

and Elementary Diagrams



PILOT DEVICES



Pilot Devices:Pushbuttons

• A pushbutton is a control device used to

manually open and close a set of contacts.

• Pushbuttons are available in a flush mount,

extended mount, with a mushroom head,

illuminated, or non-illuminated.

• Pushbuttons come with either normally

open, normally closed, or a combination

contact block.



Pilot Devices: Selector switches

• Selector switches are also used to manually

open and close contacts. Selector switchescan be maintained, spring return, or key

operated.

• Selector switches are available in 2-, 3-, and4-position types.



Pilot Devices: Pilot lights

• Pilot lights provide visual information of the

circuit’s operating condition.

• Pilot lights are normally used for ON/OFF

indication, caution, changing conditions, and

alarm signaling.

• Pilot lights are available with a variety of lens

colors, such as red, green, amber, blue, white,

or clear.



WIRING VS SCHEMATIC DIAGRAMS



WIRING DIAGRAM• A wiring diagram shows, as closely as possible,

the actual location of all component parts of the device.

• The open terminals (marked by an open circle)

and arrows represent connections made bythe user.

• Since wiring connections and terminalmarkings are shown, this type of diagram is

helpful when wiring the device or tracingwires when troubleshooting.



WIRING DIAGRAM

• Bold lines denote the power circuit and thin

lines are used to show the control circuit.Black wires are conventionally used in power

circuits and red wire in control circuits for AC

magnetic equipment.



SCHEMATIC DIAGRAM

• An elementary diagram is a simplified circuit

illustration.

• Devices and components are not shown in

their actual positions.

• All control circuit components are shown as

directly as possible, between a pair of vertical

lines representing the control power supply.



SCHEMATIC DIAGRAM• Components are arranged to show the

sequence of operation of the devices and howthe device operates.

• The effect of operating various auxiliary

contacts and control devices can be readilyseen.

• This helps in troubleshooting, particularly withthe more complex controllers.

• This form of electrical diagram is sometimesreferred to as a “schematic” or “line” diagram.



OVERCURRENT VS OVERLOADPROTECTION



OVERCURRENT PROTECTION

•

Overcurrent protection devices are installed inthe power circuit to protect the conductors

and may exist in the form of fuses or circuit

breakers



OVERLOAD PROTECTION

•

If one overload contact is used, an overloadon any line will cause the overload contact to

open.

• When three overload contacts are used, the

overload contacts are connected is series.

Each contact is controlled by the adjacent

overload heater.



TYPES OF CONTROL CIRCUITS



Low Voltage Release

•

The following terms are generally accepted as havingthe same meaning:A. Under voltage release (UVR)

B. Low voltage release (LVR)

C. No Voltage release (NVR)

Operation:The motor will stop when there is supply voltage failure andwill restart automatically when the supply voltage isrestored.

• The term “two-wire” control is given to this type of circuit.

• Pilot devices such as float switches, limit switches, andtemperature controls are single contact devicesrequiring two conductors.



Low Voltage Release



Low Voltage Release• The term “2-wire” control is derived from

the fact that in the basic circuit, only two

wires are required to connect the pilotdevice to the starter.



Low Voltage Protection

•

The following terms are generally accepted as havingthe same meaning:A. Under voltage protection (UVP)

B. Low voltage protection (LVP)

C. No Voltage protection (NVP)

Operation:The motor will stop when there is supply voltage failure and will NOT restart automatically when the supply voltage isrestored.

• The term “three-wire” control is given to this type of circuit.

• An auxiliary contact is connected in parallel with the startbutton. The auxiliary contacts seal in the circuit to keep thecoil energized after the start push button is released.



Low Voltage Protection



Low Voltage Protection• The term “3-wire” control is derived from

the fact that in the basic circuit, at least

three wires are required to connect thepilot devices to the starter.



Example

•A three phase, 575 V, 60 Hz, 40 Hp SquirrelCage Induction Motor is to be connected for

full-voltage starting. It has a service factor of

1.15. Ambient Temperature is 28˚C.

Nameplate current is 38 A.

• Determine:

1. FLC of the motor

2. NEMA Starter Size

3. FLA of the motor



Example 1• Solution:

1. FLC of the motorSee Table 430.250 NEC 2011 or Table 4.30.14.4 PEC

2002

Nameplate values: three phase ,575 V, 60 Hz, 40 HpFLC = 41 A

2. NEMA Starter Size:

See NEMA Motor Starter Sizing Chart

Use: NEMA Size 3

3. FLA = Nameplate Value

FLA = 38 A



Example 2

•A 3 phase, 460 V, 60 Hz, 10 Hp Squirrel CageInduction Motor is to be connected for full-

voltage starting. It has a service factor of 1.15.

Ambient Temperature is 28˚C.

Nameplatecurrent is 12 A.

• Determine:

1. FLC of the motor

2. NEMA Starter Size

3. FLA of the motor



Example

nema iec and pilot device presentation

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