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.
Table of contents
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
| Reasons | Solution |
| SFU may be in the off-condition | Check 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 condition | Reset the overload relay |
| Loose connections at the feeder end | Tight all the connections in the feeder |
| The phase sequence is wrong | If you use an electronic protection relay, the motor may fail to start if the phase sequence is incorrect. Correct the phase sequence. |
| Control circuit | check 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 Earth | check the stator winding with an insulation tester(Megger) |
| Bearings | Grease the bearing |
| Overloading | Reduce 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 stator | The 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 unbalance | Rotor unbalances cause noisy operations. The rotor should be balanced. |
| Loose coupling | Fix the coupling properly |
| Dry bearings | Re-grease the bearings |
| Misalignment | Misalignment causes noisy operations. Check horizontal, vertical, and axial vibration & correct it. |
| The belt may be too tight | In the case of belt drive, ensure proper tightening of the belt. |
Bearing overheated
| Reasons | Solution |
| Dry running of the bearing | Re-grease bearing & ensure periodic re-greasing |
| Belt too tight | The belt coupled to the motor pulley is too tight. Adjust the tension of the belt. |
| Rotor shaft bent | The poor quality of lubrication causes overheating of the bearing. Use recommended lubrication. |
| Lubrication quality | The poor quality of lubrication cause overheating of the bearing. Use recommended lubrication. |
| Foreign material in lubrication | Replace the old lubricant with a new one. |
3-phase Induction Motor Problem–Motor overheated
| Reasons | Solution |
| Motor overloading | Overloading 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 low | In 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 connections | Loose connections |
| Stator winding earth | Check stator with Megger |
Motor Starts and Stops
| Reasons | Solution |
| Switchgear may be defective | Check switch-gears |
| Loose connections | Tight all the connections |
| Timer defective | Check the control circuit timer. |
| Motor interlocking devices are faulty | Check the Speed monitor, tachometer, etc. |
Motor runs below its rated speed
| Reasons | Solution |
| Overloading | The overloading causes motor speed reduction. Reduce the load on the motor to increase the speed. |
| Low supply voltage | The 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 circuit | Check 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 surface | Check slip-ring for any surface roughness |
| Eccentric Slip-ring | Check the slip-ring for its eccentricity. |
This is all about 3-phase induction motor problems and their remedies.
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