This document discusses motor starters, their components, and troubleshooting procedures. It describes the functions of motor starters as starting and stopping motors, providing remote control, and protecting motors. It explains the types of starters and components such as contactors, overload relays, and circuit breakers. It provides details on NEMA and IEC standards for these components. Finally, it outlines the steps for troubleshooting motor starters, including using lockout/tagout procedures, test equipment, and repair and restoration.

1. Motor Starters
And Their
Trouble shooting
J Niranjan

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Introduction to Motor Starters
Functions of a Motor Starter
Starting and stopping the motor (or other device)
Provide remote control to the motor or heater
Limit the current inrush
Reverse the motor
Control the speed of the motor
Protect the motor from overloading/over-speeding
overheating or ground fault conditions

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Introduction to Motor Starters
Types of Starters
Direct On Line Starters (DOL) or Across the line
Starters
Reduced Voltage Starters – Achieved by means of
1) Solid State Devices (Soft-starters, VFD’s)
2) Auto Transformers
3) Reactors
4) Star/Delta connections

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Components of a Motor Starter
MCCB
Contactor
O/L Relay
Ground
Fault relay
CT’s for
current
indication
Motor
protection
relay
Pilot
Lamp
CBCT for E/f
protection

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Components of a Motor Starter
Main
Contactor
CPT
Ground
Fault relay
Ammeter
Pilot
Lamp
Auxiliary
Contactor
Power Transducer for
remote indication
Note: MCCB is
not shown

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Components of a Motor Starter
Contactors
Definition: An electromechanical device that opens and
closes a power circuit. Generally operated
magnetically, providing remote control, but can also
be operated manually. Power is controlled when the
contactor’s contacts open and close.
Function: To control motors (most common) and other
power circuits (e.g. transformers, heaters, lights, and
capacitors).

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Components of a Motor Starter
Contactors
There are two main types of contactors used in industrial applications
— contactors designed to NEMA standards and contactors
designed to IEC standards
Traditional NEMA contactors are designed to meet the size ratings
(00, 0, 1, 2 … 9) specified in NEMA standards. A NEMA
contactor is designed by convention with sufficient reserve
capacity to assure performance over a broad range of
applications
Traditional IEC contactors are designed to match a contactor to a
load, expressed in both the contactor’s rating and expected life.
IEC standards do not define standard sizes — the manufacturer
can choose to apply any rating based on meeting the
performance and test requirements of the IEC standards.

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Components of a Motor Starter
NEMA Contactor IEC Contactor

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Components of a Motor Starter
NEMA Contactors
for various motor
ratings

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Components of a Motor Starter
NEMA Vs IEC
Contactors for
various motor
ratings
HP @ 460V NEMA Contactor Size IEC Contactor Size
I Size 00 9A
2
5 Size 0
7.5 Size I I2A
I0 I8A
I5 Size 2 25A
20 32A
25 40A
30 Size 3 50A
40 65A
50 80A

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Components of a Motor Starter
Let’s say that an application requires a contactor for a I5HP motor
— if a NEMA device was being specified, a Size 2 contactor
would be required. The Size 2 device has much greater capacity
than is required for the application, it is capable of controlling a
25HP motor. However, if an IEC contactor is selected, a I5HP
device could be specified. Thus a physically smaller, lower cost
device can be got with IEC standard.
IEC contactors are rated much closer to the ultimate switching
capabilities and have much less “reserve capacity” than their
NEMA counterparts. This in great part contributes to the small
physical size of IEC contactors compared to NEMA contactors
(of the same horsepower rating) but the life would be much
lesser.

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Components of a Motor Starter
OVERLOAD RELAYS
Definition: Electromechanical device that prevents
damage to a motor caused by excessive current.
When an overload relay senses that a motor is
overheating (eg. drawing too much current over a
specific period of time), the overload relay will trip,
removing power to the motor (by interrupting the
contact or coil circuit).
Function: To protect the windings of motors and the
conductors to the motor against overload currents.

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Components of a Motor Starter
Traditional NEMA thermal overload relays typically accept
interchangeable, field installable heater elements. Each
overload relay will accept different heater elements based on the
maximum current rating of the overload relay or the contactor
size if the overload relay is to be directly installed on the
contactor. The heater elements are typically eutectic alloy
(although bimetal constructions are also available), and are
indirectly heated. Heater elements are available with trip
Classes 10, 20, and 30.
Traditional IEC thermal overload relays include integral, directly
heated bimetal elements. Typically these overload relays have
an adjustable current setting, marked in amperes. The
minimum to maximum adjustment range is approximately 1:1.5
(ex. 10A to 15A

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Components of a Motor Starter
NEMA Overload Relay
IEC Overload Relay

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Components of a Motor Starter
Trip Classes of IEC Overload Relays

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Components of a Motor Starter
Overload Relay- Time Current
Curves

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Components of a Motor Starter
Motor Protection Circuit Breakers
Definition: A circuit breaker that is assembled as an integral unit in
a supporting and enclosing housing of insulating material.
Thermal elements (various trip classes available, typically class
10) are ambient temperature compensated for precise overload
protection of motor windings, and include phase loss protection.

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Components of a Motor Starter
Function: Motor Protection Circuit Breakers are multi-
function devices designed to:
Manually control motors (most common) and other
power circuits
(e.g. transformers, heaters, and lights)
Protect the windings of motors and the conductors of the
motor against overload currents
Protect motor circuit components (contactors, overload
relays, and motors) and the conductors to the motor
against short circuit currents
Disconnect all of the motor circuit conductors
simultaneously from their source of supply

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Components of a Motor Starter
Short Circuit Protective Devices
There are a number of choices of short circuit protective
devices including fuses, molded case circuit breakers,
and motor circuit protectors. Even though they are
not “motor control devices” they are closely
associated with and used with motor control devices.
All Installation Codes and Standards dictate, a short
circuit protective device is required in every motor
branch circuit

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Components of a Motor Starter
Short Circuit Protective Devices
Fuses
Definition:
An overcurrent protective device with a fusible link
that operates (one-time only) to open the circuit on
an overcurrent condition.
Function:
Protect motor circuit components (contactors,
overload relays, and motors) and the conductors to
the motor against short circuit currents
Protect the motor circuit conductors against overload
currents

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Components of a Motor Starter
Short Circuit Protective Devices
Molded Case Circuit Breakers
Definition: A device that is assembled as an integral unit in a
supporting and enclosing housing of insulating
material, designed to open and close a circuit by non-
automatic means and to open the circuit automatically
on a predetermined overcurrent (short circuit or
overload), without injury to itself when properly
applied within its rating.
Function: Protect motor circuit components (contactors, overload
relays, and motors) and the conductors to the motor
against short circuit currents
Protect the motor circuit conductors against overload
currents
Disconnect all of the motor branch circuit conductors
simultaneously from their source of supply

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Components of a Motor Starter
TYPE 2 CO-ORDINATION
Type 2 Coordination means that a starter will not be
damaged in the event of a short circuit fault.
Following is the definition from IEC 60947-4-1:
Type 2 Coordination: under short-circuit conditions, the
contactor or starter shall cause no danger to persons
or installation and shall be suitable for further use.
The risk of contact welding is recognized, in which
case the manufacturer shall indicate the measures to
be taken with regard to the maintenance of the
equipment.

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Components of a Motor Starter
TYPE 2 CO-ORDINATION
By specifying Type 2 Coordination, safety to personnel is enhanced
because arc flashes resulting from short circuit faults can be
eliminated.
In addition to enhanced safety, Type 2 Coordination provides the
following benefits:
Reduced component replacement costs
Increased productivity
Simple device selection
Component replacement costs are reduced because contactors,
starters, and motor protection circuit breakers are protected against
damage — so they don’t need to be repaired or replaced after a short
circuit fault.

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Components of a Motor Starter
It is simple to select the appropriate motor control devices that
provide Type 2 Coordination - manufacturers provide easy to use
tables that match the motor protection circuit breaker and contactor
that will provide Type 2 coordination up to a specified short circuit
fault current. The table provided by Siemens is in the next slide

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Components of a Motor Starter

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Troubleshooting of Motor Starters
• COLLECT SCHEMATIC DIAGRAMS, SPECIFICATIONS AND
TROUBLESHOOTING AIDS
• PREPARE THE HWP
• CONDUCT DIAGNOSTIC TROUBLESHOOTING
This should be done in the following steps:
Have the correct prints or drawings on hand
Verify the meter is in good condition, no cracks in the leads, fresh
batteries and recent calibration
Put on the appropriate PPE. Carefully open the doors or remove
the equipment covers
Test the meter on a known external source
Read the Voltage (or Absence) on the load side of the circuit
breaker for the starter, phase to phase first, then phase to ground
Check for control Voltage or any other Voltage (possibly from other
circuits) within the starter
Record the readings
Upon completion of the troubleshooting or repair, close the doors
and replace all covers—Do not leave energized equipment
unattended

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Troubleshooting of Motor Starters
• LOCATE THE POWER SOURCE AND REMOVE POWER
This step amounts to de-energizing the circuit.
The supply for the starter is likely the main circuit breaker.
This is located in the module itself.
Be sure the motor is stopped before opening the main
disconnect—This will prolong the contact life of the
disconnect switch contacts; if the motor is still running, stop it
manually
If the module needs to be removed, should be done following
PPE table and standby person shall be present
Verify that all power sources are absent from the starter—Any
capacitors should be discharged and grounded
• UTILIZE LOCKOUT-TAGOUT PROCEDURES

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Troubleshooting of Motor Starters
• UTILIZE TEST EQUIPMENT TO
TROUBLESHOOT AND ISOLATE CAUSE
Troubleshooting of circuits necessitates using the
proper test equipment within its ratings. Most low
Voltage test equipment suited for industrial use is
rated at 1000 volts dc. Different types of test
equipment are used for different purposes. These
test equipments include digital multi-meter, clamp
on Ammeter, DLRO, Megger etc.

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Tests on Various Components
•Main circuit breaker –
Rarely is the problem here, however contact resistance should
be tested with a DLRO, trip time can also be tested with a high
current test set.
•Control power transformer
CPT—normally energized when circuit breaker is on. Check
fuses and continuity of primary and secondary windings.

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Tests on Various Components
Contactor coil
Measure continuity with an ohmmeter (DMM). The values will vary
depending on the contactor model. Some bigger sized contactors use
a ‘DC’ coil and hence the AC control supply is rectified and fed to the
coil. In this case the continuity cannot be checked
Auxiliary switch contacts
Measure continuity with DMM. Contacts should follow armature:
The ‘NO’ contact (‘a’ contact – has a suffix number 3-4)makes with
main , the ‘NC’ contact (‘b’ contact – has a suffix number 1-2)breaks
when main makes

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Tests on Various Components
Current Transformers
Measure for continuity with ohmmeter, make sure
leads are clean and tightly connected.

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Tests on Various Components
Ground fault relay (Contd.)
Ground fault relays must be manually reset. Causes of
ground faults are moisture, insulation damage or
deterioration, or unintentional connections of neutral
and ground conductors downstream from the main
service.
In any case, the cause of the ground fault must be
determined before the circuit is re-energized.

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TEST PROCEDURES
•SET UP A TEST CIRCUIT
One of the best means of checking out the starter or any of its
individual components is to set up a test circuit. A variac can
be used to inject this control supply. In some MCC’s, there is a
‘test’ facility, which energizes only the control supply and can
be used

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TEST PROCEDURES
•OPERATE THE TEST CIRCUIT
There are some safety rules to follow when checking
components with a test circuit.
Warning: Whenever using an external Voltage to test a
component in a starter, you must ensure that the device under
test is isolated from all other, so there is no possibility of
backfeed or accidental energization
Test circuits are easily used and operated when the device is
out of the starter and placed on the bench. However, in real
world troubleshooting, it is not always practical to take a
contactor or relay out of the MCC for testing. In fact, it is
usually prohibitive.

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Tests on Various Components
Isolate the Device—
Great care must be exercised so that the component under test
cannot energize another component, specifically, if you test the
main contactor with an external 110 Volt supply, you don’t
want the motor to actually start
Watch for Interlocks-
In a reversing starter, or a two-speed starter, the two contactors
are electrically and mechanically interlocked so that only one
can be closed at once. Again, avoid energizing an interlocked
device. Even though there may be no electrical hazard (the
input power will have de-energized) but the mechanical
linkage can be damaged by the power of a large contactor.

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REPAIR AND RESTORATION
•REPAIR CIRCUIT OR REPLACE DEFECTIVE
COMPONENT
Replace the defective device with a like device that is
either new or known to be fully operational. If there is
doubt, then the replacement unit should be tested before
installation if possible. In most cases, any circuits or
devices repaired, particularly feeders should be meggered
to verify that no conductors are shorted or grounded.
•CLEAR THE AREA AND REMOVE THE
LOCKOUT
As in the normal LOTO procedure, notify all affected
personnel that the power is about to be restored. Remove
any temporary grounds, barriers and warning signs and
remove the LOCK OUT.

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REPAIR AND RESTORATION
•RESTORE POWER
Before inserting the fuses or closing the circuit breaker, be sure all
controls are in the OFF or MANUAL positions so that equipment
does not start up when the control circuit is energized. Using the
proper techniques, close the CB (or install the fuses). Immediately
verify that control power is present and within the proper Voltage
range. (control fuses may blow due to CPT inrush and hence voltage
checking is necessary)
•TEST OPERATION
Again, any affected personnel should be notified that the starter is
about to be tested and that the motor will be starting. The motor
should be brought on in the normal mode by remote controls.

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REPAIR AND RESTORATION
•RESTORE SERVICE
Provided that the operational tests are successful, then the control
selectors can be set to the RUN or AUTOMATIC mode. When the
control circuit has been restored, then is should be observed for
proper operation.
•DOCUMENT THE REPAIR, CORRECT DRAWINGS
No job is complete until the documentation is done through 7i. Any
changes made in wiring to accommodate new components should be
marked in on the schematic diagram and highlighted in a different
color ink (red).
If required, a RCA (root cause analysis) should be conducted
immediately.