Different Faults in Three Phase Induction Motor & their Remedies

This article describes different types of faults and problems in 3-phase induction motor & their remedies. The induction motor is a very robust, reliable, and maintenance-free motor. We can enhance the life span of the motor by doing periodic maintenance.

A 3-phase induction motor is the most reliable and functions without problems if we operate the motor within its operating criteria. The motor is most vulnerable if we operate it under overload conditions.

The overloading causes the motor to take more current. The motor draws a current that is more than its rated current, causing winding heat up and, eventually, insulation failure. The intermittent overloading makes the insulation deteriorate over some time. Increased atmospheric temperature also hinders the proper cooling of the motor & it eventually reduces the life of the insulation.

Whatever factors increase the temperature rise and reduce the motor’s cooling is vulnerable to motor operation.

Now, we will discuss the problems and faults of the 3-phase induction motor.

3-Phase Induction Motor Problems – Possible Faults and Remedies

There are the following different problems of 3-phase induction motor & their remedies

Motor fails to start

SFU may be in the off-conditionCheck the supply with a multimeter or test lamp
Check the SFU, and make it on.Check the SFU, and make it on
Overload relay may be in the trip conditionReset the overload relay
Loose connections at the feeder endTight all the connections in the feeder
The phase sequence is wrongIf you use an electronic protection relay, the motor may fail to start if the phase sequence is incorrect. Correct the phase sequence.
Control circuitcheck the control circuit and find the cause of the non-operation of the main contactor.
Stator or Rotor winding open Check the stator winding with the help of a 4 & 1/2 -digit multimeter. If the winding resistance is infinite, replace the motor with a new one.
Stator Earthcheck the stator winding with an insulation tester(Megger)
BearingsGrease the bearing
OverloadingReduce the load on the motor

Motor Noisy operation after start

Reasons Solution
Single phasing The single phasing may occur because of (1) one of the three fuses blown. (2) the contactor pole open. (3) motor winding open. Under single phasing, the motor draws more current and produces noise.
Rubbing of the rotor with statorThe stator and rotor have physical separation, and the gap between the stator & rotor is called the air gap. The rubbing may be caused by an unbalanced magnetic pull(UMP) or due to other mechanical reasons.
Rotor unbalanceRotor unbalances cause noisy operations. The rotor should be balanced.
Loose coupling Fix the coupling properly
Dry bearingsRe-grease the bearings
Misalignment Misalignment causes noisy operations. Check horizontal, vertical, and axial vibration & correct it.
The belt may be too tightIn the case of belt drive, ensure proper tightening of the belt.

Bearing overheated

Reasons Solution
Dry running of the bearingRe-grease bearing & ensure periodic re-greasing
Belt too tightThe belt coupled to the motor pulley is too tight. Adjust the tension of the belt.
Rotor shaft bentThe poor quality of lubrication causes overheating of the bearing. Use recommended lubrication.
Lubrication qualityThe poor quality of lubrication cause overheating of the bearing. Use recommended lubrication.
Foreign material in lubricationReplace the old lubricant with a new one.

3-phase Induction Motor ProblemMotor overheated

Reasons Solution
Motor overloadingOverloading causes an increase in current & it causes motor heating. Finally, it affects the life of insulation.
Reduce the load.
Poor ventilation
The improper ventilation increases the winding temperature, which causes more heating in the winding. Therefore, maintain the proper ventilation.
Supply voltage too high or lowIn this condition, the motor draws more current than its rated current. It causes overheating of the core and winding of the motor. Therefore, Ensure supply voltage within the rated supply voltage of the motor.
Loose connectionsLoose connections
Stator winding earthCheck stator with Megger

Motor Starts and Stops

Reasons Solution
Switchgear may be defectiveCheck switch-gears
Loose connectionsTight all the connections
Timer defectiveCheck the control circuit timer.
Motor interlocking devices are faultyCheck the Speed monitor, tachometer, etc.

Motor runs below its rated speed

Reasons Solution
OverloadingThe overloading causes motor speed reduction. Reduce the load on the motor to increase the speed.
Low supply voltageThe torque of the motor depends on the voltage. The torque reduces with a decrease in the supply voltage. In this condition, the motor may not be able to cater to the load torque & the speed of the motor decreases.
Ensure the supply voltage should be within the motor operating voltage range.

Motor Runs at a Slow Speed when External Resistance is cut in the case of a Slip-Ring Induction Motor.

Reasons Solution
Rotor open circuitCheck the Rotor winding of the slip ring induction motor
Open Brushes Check the brushes for their proper contact with the slip-ring.
The rough Slip ring surfaceCheck slip-ring for any surface roughness
Eccentric Slip-ringCheck the slip-ring for its eccentricity.

This is all about 3-phase induction motor problems and their remedies.

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