MOTOR TESTING BENCH
STANDARD TESTING PROCEDURES
DEPARTMENT OF ELECTRICAL ENGINEERING
1. Introduction: .......................................................................................................................... 2
1.1 Testing Overview: ............................................................................................................... 3
PPE Requirements: ................................................................................................................... 3
2. Visual Inspection: ................................................................................................................. 3
3. Measurement of Coil Resistance ......................................................................................... 4
3.1 Three Phase Motor ......................................................................................................... 4
3.2 Single Phase Motor ......................................................................................................... 4
4. Measurement of Insulation Resistance ............................................................................... 4
6. No Load Test: ........................................................................................................................ 6
7. ON Load Test......................................................................................................................... 8
Appendix A: Resistance Measurement using UT3516 ........................................................... 8
1. Introduction:
This document provides a comprehensive step-by-step guide for testing single-phase and threephase induction motors using the motor testing bench at GIFT University Gujranwala. Proper
testing of motors is essential to ensure their optimal performance, efficiency, and reliability. By
following this testing procedure, technicians and engineers can accurately assess the electrical
and mechanical characteristics of the motors and identify any potential issues or deviations from
the motor's rated specifications.
The motor testing procedure outlined in this document covers both single-phase and threephase induction motors. It includes instructions for preparing the motor testing bench,
connecting the motors, measuring and recording relevant parameters, calculating efficiency,
and ensuring safety throughout the testing process. By adhering to these guidelines, users can
obtain reliable test results, make informed decisions about motor performance, and address any
concerns or anomalies that may arise.
It is crucial to prioritize safety precautions during motor testing, including the use of appropriate
personal protective equipment (PPE) and adherence to electrical safety practices.
By following this motor testing procedure, technicians and engineers can confidently evaluate
the performance of single-phase and three-phase induction motors, troubleshoot any potential
issues, and ensure the motors' compliance with the specified standards and requirements.
Accurate testing results are crucial for effective motor maintenance, repair, and overall system
reliability.
Note: This document assumes a basic understanding of electrical systems and motor operation.
If you have any uncertainties or encounter complex motor issues during the testing process, it is
advisable to seek guidance from qualified professionals or consult the relevant technical
documentation.
1.1 Testing Overview:
Motor testing bench is basically an apparatus used for measuring different parameters of
motors; it includes its mechanical and electrical characteristics.The apparatus of testing bench
is as under :
In this there is a motor under test Firstly it is important to follow the safety precautions while
testing the motor.For motor Input parameters we use Energy Analyzer (see section 5.1) that
gives us the Input Power, Voltage, Current, Frequency and Phase degree. For Motor output
parameters use torque sensor (see section 5.2) like Torque, speed and Output Power we use
the Dynamic Torque Sensor. For measuring the force, moment of force (torque), or power use
dynamometer. We perform test on load test and no load test in no load test we find three losses
stator I2R loss, Friction and windage loss, and core loss as discussed (see section 6)
In the on load test the motor is attached to a torque sensor we give load through 5 heaters of
rating 7 kW.
1.3 PPE Requirements:
1- Take all reasonable steps to safeguard the HEALTH and SAFETY of themselves and all
other users and visitors.
2- Be sure that all equipment is properly working before using.
5. Keep a safe distance from the circuit breakers, electric circuits or any moving parts
during the experiment.
3- Avoid any part of your body to be connected to the circuit and ground.
4- Switch off the equipment and disconnect the power supplies from the circuit before leaving .
5- Observe cleanliness and proper housekeeping of the equipment and other related
accessories.
6- Wear safety gloves and goggles.
7-Make sure the wires connected should not be loose.
2. Visual Inspection:
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Inspect the motor from each side to check for any deformities of the motor outer body.
If the motor is not braked, rotate the motor shaft by hand to ensure free movement.
○ If the shaft doesn’t move freely, do not proceed to motor testing and contact the
supplier.
Take 5 pictures of the motor from the following angles.
○ Front
○ Back
○ Both Sides
○ Name Plate
Record the motor parameters given on the name plate in the motor testing chart.
3. Measurement of Coil Resistance
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Open the motor terminal box to reveal the motor coil winding.
Record the motor resistance using the UT3516 Resistance Meter. Refer to Appendix A
for the measurement procedure for UT3516 Motor.
3.1 Three Phase Motor
For three phase motors measure the resistance of each of the motor coils u1-u2, v1-v2, and
w1-w2. This measurement can be made directly if the motor is star connected. In case of delta
connections, remove the connector plates to measure the resistance.
3.2 Single Phase Motor
For single phase motors remove the capacitor wires to measure the resistance between each of
the three wires.
4. Measurement of Insulation Resistance
To measure the insulation resistance we use an insulation resistance tester while measuring IR
one terminal of the tester is placed at any one of the coils and the other terminal is placed at the
motor body.
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Set the voltage ratings at winding rated voltage.
Connect one terminal of the insulation resistance tester with any of the coil winding and
the other with the body of the motor.
Press the test button.
Observe the readings of insulation resistance.
Guidelines for dc voltages to be applied during insulation resistance
test as per IEEE 43-2000 Insulation Resistance Testing
Winding Rated Voltage (V)
Insulation Resistance direct
voltage (v)
<1000
500
1000-2500
500-1000
2501-5000
1000-2500
5001-12000
2500-5000
5. Measuring equipments:
The following equipment that we use for measuring different parameters.
5.1 Energy Analyzer (ziegler ZAM LC60):
For motor Input parameters we use Energy Analyzer that gives us the Input Power,
voltage, Current, Frequency, and Phase angle.
5.2 Torque sensor (DYN-200)
For Motor output parameters like Torque, speed, and Output Power we use the
Dynamic Torque Sensor.
6. No Load Test:
This test is performed by running the machine as a motor at rated voltage and frequency with no
connected load. After making connections we Note down the readings. For input parameters (
input power, voltage, and current ) we use an energy Analyzer (see section 5.1). And for output
parameters (speed, torque, and output power) we use a torque sensor (see section 5.2).
We perform this test at No load condition. No_Load means the motor is not coupled with a
dynamic torque sensor and DC Generator. In this way, all the input power is the total of the
losses. These losses consist of the stator I2R, friction (including brush-friction loss on
wound-rotor motors), windage, and core losses. And then we run this test and read voltage,
current, and power input at the rated frequency.
At no load, there is no output because all the input parameters are converted to
losses. and there is no output power at the output.
6.1 Friction & Windage loss:
Friction and windage loss are the two types of mechanical losses that occur due to the rotation
of the motor.
6.1.1 Identification of Friction & Windage loss:
● Supply the power to motor
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Note the readings of Voltage, current and input power at rated frequency.
Subtract the stator I2R loss from input power.
Power=input power - Stator 𝐼 2 𝑅 Loss
Power = √3𝑉𝐼 𝑐𝑜𝑠𝜙 -𝐼 2 𝑅
Plot the power vs Voltage square curve at different supply voltages (Voltages may be
vary using VARIAC).
Extrapolate the curve to V2 = 0.
The intercept with the zero voltage axis is the friction and windage loss.
6.2 Core Losses:
Core loss in an induction motor is the heat loss that gets dissipated in the core of the motor due
to the alternating magnetic field created by the stator winding.
6.2.1 Identification of Core Loss:
The core loss, Ph, at each test voltage, is obtained by subtracting the value of friction and
windage loss (determined in 5.1.1) from the input power minus stator I2R loss.
Core loss= Input power-I2R loss-friction & Windage loss.
Core loss= √3𝑉𝐼 𝑐𝑜𝑠𝜙 -𝐼 2 𝑅-F&W Loss.
6.3 Stator I2R Loss:
Stator I2R losses, also known as stator copper losses, are a type of copper loss in an induction
motor that occur due to the resistance of the stator windings. These losses result from the flow
of current through the stator windings, causing power dissipation in the form of heat.
When an alternating current flows through the stator windings, the resistance of the winding
material leads to power loss, given by the equation:
Stator I2R Loss = I^2 * R
where:
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It is the root mean square (RMS) value of the stator current.
R is the resistance of the stator winding.
7. ON Load Test
The on-load Test can be performed when the load is connected. In the ON load Test the load
increases and speed decreases. For input power, voltage, and current we use an energy
analyzer. and for output parameters (speed, torque, and output power)we use a torque sensor.
And finally we calculate the efficiency of the motor using input and output power.
In the load test Readings of electrical power, current, voltage, frequency, speed or slip, torque,
stator winding temperature or stator winding resistance, and the ambient temperature shall be
obtained at each load point. In loading the machine, start at the highest load value and move in
descending order to the lowest.
The calculations for the ON-LOAD test are as under.
Graph of speed vs torque graph:
Appendix A: Resistance Measurement using
UT3516
In coil resistance measurement we first check its inside connections. It consists of three
windings u1-u2,v1-v2, and w1-w2, and then we check the winding connections,
that is they are connected in star connection or delta. In star connection the same ends of three
coils are connected to create a neutral point in which u1 is connected to u2,v1 is connected to
v2, and w1 is connected to w2. We use a 4 probe resistance meter to measure the coil
resistance
RESISTANCE METER:
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After all connections of the coil winding press the test button and observe the reading.
STAR CONNECTION:
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First coil is u1-u2 and u1 is connected to u2, one probe of 4 probe resistance meter is
placed at u1 and the other is placed at u2. And check the resistance of the first coil
v1 is connected to v2 and uses a resistance meter to check the resistance of the second
coil, one probe is placed at v1 and the other is placed at v2.
W1 is connected to w2 and uses a resistance meter to check the resistance of the third
coil; one probe is placed at w1 and the other is placed at w2.
DELTA CONNECTION:
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For measuring the coil resistance of the first coil winding u1 is connected to u2 through
a resistance meter one probe is placed at u1 and the other is placed at u2.
For measuring the coil resistance of second coil winding v1 is connected to v2 the
resistance of the second coil winding one probe is placed at v1 and the other is placed at
v2.
For measuring the coil resistance of third coil winding w1 is connected to w2 for
measuring the resistance of third coils winding one probe is placed at w1 and the other
is placed at w2.
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