6 Common Electric Motor Failures and Solutions

Figure 1: An Electric Motor.

Electric motors are widely applied in production, transmission, and distribution. But failures could occur due to wrong operation, insufficient maintenance, etc. Here, 6 common types of electric motor failures and their solutions will be introduced as follows.

1. Abnormal Start of the Motor

1) Check switches, melts, contact points and motor leads;
2) Heat the broken part to the temperature as high as allowed by the insulation grade to soften the paint. Then lift the wire and repair the broken part with the same specification wire. Wrap it with insulation, and paint and dry it;
3) Do the same as above with an extra step of insulating the grounding or short-circuit parts, and then painting and drying;
4) In accordance with the wiring diagram, heat the end and reconnect it correctly (including binding, insulating treatment and painting);
5) Acquire a new melt according to the motor specification;
6) Correct the wiring.

2. The Motor Overheating or Smoking

1) Check the applied mechanical load for friction or jamming; 2) Check whether the mechanical load increases. If so, reduce the load until the temperature is normal; 3) Check whether the motor ventilation system is faulty and reduce the load at the same time; 4) Check whether the current of each phase of the motor is balanced, and see if the stator winding is faulty or the phase is missing.

Figure 2: Components of an electric motor in sectional view.

3. Abnormal Vibration or Noises of the Motor

3.1 Abnormal Vibration of the Motor

1) Overhaul or replace with new bearings;
2) Check the cause of vibration and re-compress the iron core for processing;
3) Measure the power supply voltage. Check the cause of excessive voltage and unbalance, and deal with it if necessary;
4) Clean the bearing and add grease to make it fill 1/2~2/3 of the volume of the bearing chamber;
5) Repair fans and hoods to the correct size; clean air ducts;
6) Adjust the air gap to improve the assembly quality.

3.2 Abnormal Noises of the Motor

Figure 3: Frequency distribution of different motor faults.

1) Mechanically: the bearing sound is abnormal. If it is caused by lack of oil, refuel it immediately; if the bearing is damaged, stop the operation immediately.
2) Electrically: check whether the voltage and frequency are normal and whether the three-phase stator current is balanced. See if there is disconnection or an inter-turn short circuit inside the winding.

4. Electrified motor shell

1) Connect the power cord as well as ground wire correctly;
2) Dry the motor and replace the aging insulation;
3) Wrap or replace the lead wire insulation and repair the junction box.

5. The Motor Operating with a Phase Failure

Check whether it is a phase failure or a fault in the motor stator circuit. There are two ways to prevent a phase failure. One is to rely on the judgment and immediate handling of the watchman; the other is to install a phase-loss protector in the motor circuit.

6. Low Insulation Resistance of the Motor

1) If the winding is damp or wet with water, heat and dry it;
2) If the winding insulation can continue to work after being tested, clean, dry and repaint it; if the insulation is aging and cannot be operated safely, replace it.

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