DR.

BABASAHEB AMBEDKAR MARATHWADA UNIVERSITY AURANGABAD,

MAHARASHTRA

PEOPLE’S EDUCATION SOCIETY’S (MUMBAI)

P.E.S. COLLEGE OF ENGINEERIN AURANGABAD

Department of Electrical Engineering
T. E. [EEP]

A seminar Report on
“Single phase Motor Testing”

SUBMITTED BY
Mohammad Baseer Faisal

GUIDED BY
Prof.N.D. Kakde
DEPARTMENT OF ELECTRICAL ENGINEERING
(2018-2019)
 ACKNOWLEDGEMENT

I express my sincere gratitude to my concerned teacher and guide Prof Mr. Prof. N.D.
Kakde , Professor, Department of Electrical Engineering, for his valuable and
inspiring guidance towards the progress on the topic “Single Phase Motor Testing”
and providing valuable information for the development of my report.
Last but not the least I express my sincere and hearty thanks to all those who have
directly or indirectly helped me in completing this seminar presentation and report
successfully.

Date:
 CERTIFICATE

This is to certified that Mohammad baseer Faisal has successfully completed the project work
entitled “Single phase motor testing” And the presented successfully in partial fulfillment of
Bachelor of engineering during academic year 2018-2019 in Department of Electrical
Engineering of P.E.S. College of Engineering.

Guided By:- Head f Department:-

Prof. N.D. Kakde Dr. B.Chaudhari
 INDEX

1. INTRODUCTION OF SINGLE PHAS MOTOR

2. NEED OF TESTING

3 .TYPES OF TESTS

a) INSULATION TESTING
b) WINDING TESTING
c) BLOCK ROTOR TESTING
d) NO LOAD TESTING

e) ROUTINE TESTING
f) SPECIAL TESTING
g) NO LOAD RUNNING TESTING

4.MISCELLENOUS TESTING
INTRODUCTION

An induction motor or asynchronous motor is an AC electric motor in which the electric current
in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic
field of the stator winding.[1] An induction motor can therefore be made without electrical
connections to the rotor.[a] An induction motor's rotor can be either wound type or squirrel-cage
type.

Three-phase squirrel-cage induction motors are widely used as industrial drives because they are
self-starting, reliable and economical. Single-phase induction motors are used extensively for
smaller loads, such as household appliances like fans. Although traditionally used in fixed-speed
service, induction motors are increasingly being used with variable-frequency drives (VFDs) in
variable-speed service. VFDs offer especially important energy savings opportunities for existing
and prospective induction motors in variable-torque centrifugal fan, pump and compressor load
applications. Squirrel cage induction motors are very widely used in both fixed-speed and
variable-frequency drive (VFD) applications

induction motor or asynchronous motor

 Why is Electric Motor Testing Done?

After bearing failure, electrical faults are the most common mode of motor failure, so in addition,
a properly planned electrical testing scheme is important for making sure of the plant reliability.
The Electric Power Research Institute (EPRI) conducted a survey which brought into the light
that, 48% of motor failures are because of electrical failures. The 48% can be again divided into
rotor problems (12%) and winding problems (36%). The other 52% of failures are mechanical
faults.

Many diagnostic tools, such as clamp-on ammeters, temperature sensors, a Megger or oscilloscope, can
help illuminate these issues.

Winding defects occurs due to contamination, ageing of insulation, thermal overload, power surges,
damaged wire/materials, and other causes. They start as energy crossing an insulation fault like moisture,
which sets apart at least one turn. This creates extra stress and increase in temperature across the fault,
which increases until the winding fails.
Some of the winding faults are:

Between turns in a coil

Between coils in a phase
Between coils in different phases
Between a coil or phase and ground

Fault finding of at least one of the above can save your facility countless hours of shut down and
numerous dollars in savings.
 Types of Testing:-

There are several types of single phase motors. What is however common to them all is that they have a
Start Winding, a Run Winding, and a Common connection between them as shown below:
Testing of single phase motors is pretty easy if certain basic steps are followed. The objective of any AC
motor test is to determine the health status of the motor. The basic steps in ascertaining the health of any
motor are given below
(a) General Inspections
(b) Earth Continuity and Resistance Test
(c) Power Supply Test
(d) AC Motor Winding Resistance Test
(e) Insulation Resistance Test
(f) Running Amps Test
General Inspections
For the single phase motor, do the following:

(1) Check the appearance of the motor. Check for burnt, damage to body or cooling fan or shaft.
(2) Manually rotate motor shaft to examine bearing condition. Look out for smooth and free shaft
rotation. If shaft rotation is free and smooth, bearing is possibly in good condition, otherwise consider
replacing.
(3) As with all testing and inspections, the motor name plate provides valuable information that will help
to ascertain the true health of the motor. Examine the name plate thoroughly.

Earth Continuity and Resistance Test

With a multimeter, measure the resistance between motor frame (body) and earth. A good motor should
read less than 0.5 ohms. Any value greater 0.5 ohms indicate trouble with the motor.

Power Supply Test

For single phase motors, the expected voltage is about 230V or 208V depending whether you are using
the UK or America voltage system. Check that the correct voltage is applied to the motor.

AC Motor Winding Resistance Test

Check the motor winding resistance or ohms reading with a multimeter. Since there are three terminals –
S, C, R –in a single phase motor, measure winding resistance:
C to S, C to R and S to R. Measured Value S to R should be = C to S + C to R
As a rule to single phase motors, the following applies:
(1) Ohms reading between S and R should give the maximum reading of resistance
(2) Ohms reading between C and R should give the lowest reading of resistance
(3) Ohms reading between C and S should give some intermediate value between that for S to R and C to
R
Any deviation signifies a possibly bad electric motor or a motor that requires repairs.

Insulation Resistance Test

Insulation resistance failure of an electric motor is one of the first signs that the motor is about to fail.
Insulation resistance is usually measured between motor windings and earth using an insulation tester or
megometer. Set the voltage setting of the insulation resistance tester to 500V and check motor windings
to earth. Check C to E, S to E, R to E. Minimum test value for a good electric motor is at least 1MΩ

Running Amps Test

With the motor running, check the full load amps (FLA) with a suitable meter or preferably a clamp on
meter and compare with the motor name plate FLA. Deviations from rated FLA could signify problems
with the motor under test.
 Insulation Testing:-

To prolong the life of electrical systems and motors, regular insulation resistance testing is required. Over
the years, after many cycles of operation, electric motors are exposed to environmental factors such as
dirt, grease, temperature, stress, and vibration. These conditions can lead to insulation failure, resulting in
loss of production or even fires.

An effective motor insulation resistance system has high resistance, usually (at an absolute minimum)
greater than a few mega ohms (MΩ). A poor insulation system has lower insulation resistance. The
optimal insulation resistance for an electric motor is often determined by the manufacturer’s
specifications, the criticality of the application where the motor is used, and the environment where it is
located.

It is practically impossible to
determine rules for the actual minimum insulation resistance value of an electric motor because
resistance varies according to method of construction, condition of insulation material used, rated
voltage, size and type. A general rule-of-thumb is 10 Megohm or more. The insulation system of an
electrical motor is said to be in good condition if:
Measured Insulation resistance is greater than or equal to 10MΩ

Typical Insulation Resistance Level for Electric Motors

There are no rules for determining the minimum insulation resistance value for a motor. Most data
available are empirical.

How to Measure Insulation Resistance of a Motor

The measurement of insulation resistance is carried out by means of a mega ohmmeter – a high resistance
range ohmmeter. To measure insulation resistance, a DC voltage of 500V or 1000V is applied between
the windings and the ground of the motor as shown below:

During the measurement and immediately afterwards, do not touch any terminals of the motor as some of
them carry dangerous voltages that may be fatal.
The minimum insulation resistance of motor measured to ground at 500V can be measured at a winding
temperature of -15°C – 20°C. The maximum insulation resistance can be measured at 500V with
operating windings temperature of 80-120°C depending on the motor type and efficiency

How to Calculate Minimum Insulation Resistance of Motors

The minimum insulation resistance of any motor, Rmin, can be calculated by multiplying the rated
voltage, VR, with the constant factor 0.5 MΩ /kV:
Rmin = 0.5*VR

Regular Checks of Motor Insulation Resistance The key to prolonging the life of any electrical device is
periodic checks & maintenance. The insulation resistance of stored and active motors should be checked
regularly:
(a) If the insulation resistance of a new, cleaned or repaired motor that has been stored for some time is
less then 10 MΩ, the reason might be that the windings are humid and need to be dried.
 Insulation measurement using megger

(b) For a motor in operation, the minimum insulation resistance may drop to a critical level. If the
measured value of insulation resistance is greater than the calculated value of minimum insulation
resistance, the motor can continue to run. However, if it drops below this limit, the motor has to be
stopped immediately to prevent harm to personnel due to the high leakage voltage
Every 3 phase motor has six (6) terminals with the supply voltage connected to three (3) of those terminals. The
most common configuration of a three-phase motor is the Delta (∆) – Star (Wye) configuration with the Delta side
connected to supply voltage. The terminal configuration of a 3 phase motor is shown below:

Terminals Configuration of a 3 Phase Motor

The W2U2V2 terminal set is the star side of the 3 phase motor while the U1VIW1 is the Delta side of the motor
connected to the supply voltage.

The 3 phase motor is a rugged piece of equipment but as with everything man made, there comes a time when this
beautiful piece of machinery fails either due to old age, misapplication, mal-operation or any other adverse cause.

The most common failure mode of a 3 phase AC motor is burnt winding or shorted winding leading to the damage
of the motor. Often it is required to test the winding of the 3 phase windings with the aid of a multimeter or
ohmmeter to determine whether the motor is still good or burnt or shorted.

How to Test the Winding of a 3 phase Motor

To determine whether a 3 phase motor is still good or has gone bad, a simple ohmmeter test across the windings of
the motor will reveal its true state of health. As shown below, the indicated terminal matrix (blue lines) shows the
way the windings of a 3 phase motor should be tested with an Ohmmete

How to test the windings of a 3 Phase Motor with an Ohmmeter

r:

The first thing to do before testing the windings of the motor is to remove the links linking terminals W2U2V2 and
the disconnect the motor from supply (L1, L2, L3). A multimeter terminals placed across this matrix of terminals
will indicate the following readings for a good 3 phase motor:
(a) Terminals W1W2, U1U2, V1V2 will indicate continuity for a good motor
(b) Every other terminal combinations should indicate Open for a good motor
(c) Readings between any of the six (6) terminals and the motor frame signifying earth
(E) should indicate open for a good motor.

Ohmmeter Readings for a Bad 3 phase Motor

In the case of a burnt or bad 3 phase motor, this matrix of terminals should indicate the opposite readings for a bad
motor:
(a) If any of the terminal combinations W1W2, U1U2, V1V2 should indicate open then
the motor is bad.
(b) If any other terminal combinations should indicate continuity instead of open, then
the motor is bad.
(c) If the reading between any of the six (6) terminals and motor frame (E) should
indicate continuity, then the motor is dead.
Ohmmeter Readings for a Bad 3 phase Motor
The 6920 motor rotor test system collocates the multi-channel special fixture of the 6905 and the 6920
and the 6908 24/48 could integrate the testing problems together in one time. It serves as an edged tool of
inspection to engineering, quality control and manufacturing sectors. Applications include various motor,
for example: fan motor or vehicle motor.

Standard system is the Super Space-Saving Desktops Tester.

Optional system is the Systematic Modular Cabinet Tester.

Routine tests

The primary purpose of the routine test is to insure freedom from electrical and mechanical defects, and
to demonstrate by means of key tests the similarity of the motor to a "standard" motor of the same design.
The "standard" motor is an imaginary motor whose performance characteristics would agree exactly with
the expected performance predictions.

Depending on the size of the motor, some or all of the following tests could constitute routine tests:

 Winding resistance measurement

 No-load running current and power
 High-potential test
 Locked-rotor test
 Air-gap measurement
 Direction of rotation and phase sequence
 Current balance
 Insulation resistance measurement
 Bearing temperature rise
 Magnetic center at no-load
 Shaft voltages
 Noise
 Vibration

NEMA MG1 includes the first three tests for all motors, and the fourth test for medium motors only.

Prototype tests

The purpose of a prototype test is to evaluate all the performance characteristics of the motor. This test
consists of the following tests in addition to the routine tests:

 No-load saturation characteristic

 Locked rotor saturation characteristic
 Locked rotor torque and current
 Loss measurement including stray load loss
 Determination or measurement of efficiency
 Temperature rise determination
 Surge withstand test

No-load running...
Testing electric motors doesn’t have to be a mystery. Knowledge of the basics together with powerful
new test equipment vastly simplifies the job.

Electric motors have had a reputation for being a mix of science and magic. So when a motor fails to
operate it may not be obvious what the problem is. Knowing some basic methods and techniques along
with having a few test instruments handy helps detect and diagnose problems with ease.

Testing electric motors doesn’t have to be a mystery. Knowledge of the basics together with powerful
new test equipment vastly simplifies the job.

Electric motors have had a reputation for being a mix of science and magic. So when a motor fails to
operate it may not be obvious what the problem is. Knowing some basic methods and techniques along
with having a few test instruments handy helps detect and diagnose problems with ease.

No-load running. test

When an electric motor fails to start, runs intermittently or hot, or continually trips its overcurrent device,
there my be a variety of causes. Sometimes the trouble lies within the power supply, including branch
circuit conductors or a motor controller. Another possibility is that the driven load is jammed, binding or
mismatched. If the motor itself has developed a fault, the fault may be a burnt wire or connection, a
winding failure including insulation deterioration, or a deteriorating bearing.

A number of diagnostic tools, such as clamp-on ammeters, temperature sensors, a Megger or

oscilloscope, can help illuminate the problem. Preliminary tests generally are done using the ubiquitous
multimeter. This tester is capable of providing diagnostic information for all kinds of motors.

Electrical measurements
If the motor is completely unresponsive, no ac humming or false starts, take a voltage reading at the
motor terminals. If there is no voltage or reduced voltage, work back upstream. Take readings at
accessible points including disconnects, the motor controller, any fuses or junction boxes, and so on, back
to the over-current device output at the entrance panel. What you’re looking for is essentially the same
voltage level as measured at the entrance panel main breaker.

When there is no electrical load, the same voltage should appear at both ends of the branch circuit
conductors. When the circuit electrical load is close to the circuit capacity, the voltage drop should not
exceed 3% for optimum motor efficiency. In a three-phase hookup, all legs should have substantially
equal voltage readings, with no dropped phase. If these readings vary by a few volts, it may be possible
to equalize them by rolling the connections, taking care not to reverse rotation. The idea is to match
supply voltages and load impedances so as to balance the three legs.

If the electrical supply checks out, examine the motor itself. If possible, disengage the load. This may
restore motor operation. With power disconnected and locked out, attempt to turn the motor by hand. In
all but the largest motors the shaft should turn freely. If not, there is an obstruction inside or a seized
bearing. Fairly new bearings are prone to seizure because the tolerances are tighter. This is especially true
if there is ambient moisture or the motor has been unused for a while. Often good operation can be
restored by oiling front and rear bearings without disassembling the motor.

If the shaft turns freely, set the multimeter to its ohms function to check resistance. The windings (all
three in a three-phase motor) should read low but not zero ohms. The smaller the motor, the higher this
reading will be, but it should not be open. It will usually be low enough (under 30 Ω) for the audible
continuity indicator to sound.

Digital Multimeter

A DMM (digital multimeter), such as this Keithley DMM7510 from Tektronix, is a must-have instrument
for motor testing. A wide range of DMMs are available to measure voltage, current, and resistance,
depending on the motor power ratings.

Small universal motors, such as those used in portable electric drills, can contain extensive circuitry
including a switch and brushes. In the ohmmeter mode, connect the meter to the plug and monitor the
resistance as you wiggle the cord where it enters the enclosure. Move the switch from side to side and,
with a trigger switch taped so it remains on, press on the brushes and turn the commutator by hand. Any
fluctuation in the digital readout may point to a defect. Often a new set of brushes is what’s needed to
restore operation.

Amperage or current readings are useful in motor testing as well. With a voltage reading, you know the
electrical energy available at the terminals, but you don’t know how much current flows. Multimeters
always have a current function, but there are two problems with it. One is that the circuit under
investigation must be cut open (and later restored) to put the instrument in series with the load. The other
difficulty is that the typical multimeter is not capable of handling the amount of current present in even a
small motor. All the current would have to flow through the meter, burning the probe leads if not
destroying the entire instrument.

An essential tool for motor current measurement is the clamp-on ammeter. It circumvents such
difficulties by measuring the magnetic field associated with the current, displaying the result in a digital
or analog readout calibrated in amperes.
 Clamp Meter

Multifunction instruments, such as this CM174 clamp meter from FLIR, give test engineers the power of
multiple instrument functions in one unit. The CM174 features Infrared Guided Measurement (IGM
technology powered by an integrated FLIR Lepton thermal imaging sensor, giving users extra visual data
to help in troubleshooting.

Clamp-on ammeters are user friendly. Just open the spring-loaded jaws, insert either the hot or neutral
conductor, then release the jaws. The wire need not be centered in the opening and it’s OK if it passes
through at an angle. However, an entire cable containing hot and neutral conductors cannot be measured
this way. That’s because the current flowing through the two wires travels in opposite directions so the
two magnetic fields cancel out. Consequently, it’s not possible to measure the current in a power cord, as
is often desired. The use of a splitter fixes the problem. This is a short extension cord of adequate rating
with about six inches of jacket removed so that one of the conductors can be separated and measured.

Digital and legacy analog clamp-on ammeters work well and are capable of measuring up to 200 A,
which is adequate for most motor work.

The basic procedure is to measure the start-up and running current for any motor while it’s connected to a
load. Compare the reading to documented or nameplate specifications. As motors age, the current drawn
generally rises because winding insulation resistance drops. Excess current causes heat, which must be
dissipated. Insulation degradation accelerates until there’s an avalanche event, causing motor burn out.

The clamp-on ammeter reading will tell you where you stand on this continuum. In an industrial facility,
as part of routine motor maintenance, periodic current readings can be taken and put into a log posted
nearby so damaging trends can be spotted in advance to avoid expensive downtime.

Insulation testing
The insulation resistance tester (or megohmmeter), generally known by its trade name Megger, can
provide critical information regarding the condition of motor insulation. In an industrial facility, the
recommended procedure is to perform periodic tests and record the results so damaging trends can be
detected and corrected to prevent an outage and extensive downtime.

The insulation resistance tester resembles a conventional ohmmeter. But rather than the typical three-volt
test voltage derived from an internal battery and present at the probes, the Megger provides a much
higher voltage applied for a proscribed length of time. The leakage current through insulation, expressed
as resistance, is displayed so it can be graphed. This test may take place on installed or on-the-reel cable,
tools, appliances, transformers, power distribution subsystems, capacitors, motors and any type of
electrical equipment or wiring.

The test may be non-destructive, for in-service equipment, or prolonged at elevated voltage to test
prototypes to the point of destruction. A bit of a learning curve is involved in using the Megger. The
correct settings, connection procedures, test durations and safety precautions must be implemented to
avoid damaging the equipment or electrocuting the operator or coworkers.

The motor under test must be powered down and disconnected from all equipment and wiring that’s not
to be included in the test. Besides invalidating the test, such extraneous equipment could be damaged by
the applied voltage. Additionally, unsuspecting individuals could be exposed to hazardous high voltages.

All wiring and equipment has an inherent amount of capacitance, which is generally significant in large
motors. Because the equipment is in effect a storage capacitor, it’s essential that lingering electrical
energy be discharged before and after each test. To do this, shunt the relevant conductor(s) to ground and
to each other before reconnecting the power source. The unit should be discharged at least four times as
long as the test voltage was applied.

The Megger is capable of applying different voltages, and the level should be coordinated with the type
of equipment under test and the scope of the inquiry. The test generally applies between 100 and 5,000 V
or more. A protocol involving voltage level, time duration, intervals between tests and connection
methods must be composed, taking into account the type and size of the equipment, its value and role in
the production process and other factors.

Motor testing equipment

Newer more contemporary instruments make testing even easier. For instance, test equipment such as
Fluke’s 438-II Power Quality and Motor Analyzer uses algorithms to analyze not only three-phase power
quality but also torque, efficiency and speed to determine system performance and detect overloaded
conditions, eliminating the need for motor load sensors.

Power Quality and Motor Analyzer

Using proprietary algorithms, the 438-II from Fluke measures the three-phase current and voltage
waveforms and compares them against rated specifications to calculate motor mechanical performance.

It provides analysis data for both the electrical and mechanical characteristics of the motor while in
operation. Using proprietary algorithms, the 438-II measures the three-phase current and voltage
waveforms and compares them against rated specifications to calculate motor mechanical performance.
The analysis is presented in simple readouts, making it easy to gauge the operating performance and
determine if adjustments are needed before failures cause an operational shut down.
The analyzer also provides measurements to determine a motor’s efficiency (for example, the conversion
of electrical energy to mechanical torque) and mechanical power under operating load conditions. These
measures allow for determining the motor’s in-service operating power compared to its rated power to
see if the motor is operating in overloaded condition or, conversely, if it’s oversized for the application,
energy may be wasted and operating cost increased.

Other developments include integrating multiple instrument functions into one unit. For instance, a new
thermal imaging clamp-on ammeter from FLIR has a built-in infrared camera, which gives the user a
visual indication of temperature differences and thermal anomalies.

When an electric motor fails to start, runs intermittently or hot, or continually trips its overcurrent device,
there my be a variety of causes. Sometimes the trouble lies within the power supply, including branch
circuit conductors or a motor controller. Another possibility is that the driven load is jammed, binding or
mismatched. If the motor itself has developed a fault, the fault may be a burnt wire or connection, a
winding failure including insulation deterioration, or a deteriorating bearing.

A number of diagnostic tools, such as clamp-on ammeters, temperature sensors, a Megger or

oscilloscope, can help illuminate the problem. Preliminary tests generally are done using the ubiquitous
multimeter. This tester is capable of providing diagnostic information for all kinds of motors.
Thank you