Electric motor failure stems mostly from damaged bearings or stator windings. However, there are a number of other reasons they can fail.
The most common failures in order are:
- bearing failure
- stator winding failure
- overheating
- power supply anomaly
- humidity
- contamination
- unusual mechanical loads
Bearing Failure
The main reasons for bearing failure are:
- improper lubrication
- electrical discharge across the bearing
Stator Winding Failure
Electrical insulation deteriorates at a rate that doubles for every 10°C increase in temperature.
Overheating
The reasons for overheating are numerous and include:
- overloaded
- too many starts
- high ambient temperature
- coolant failure
- low or unbalanced voltages
Power Supply Anomaly
- harmonics
- over-voltage
- under-voltage
- voltage unbalance
- voltage spikes
Humidity
If the motor is stopped and cools down it may drop below the dew point. Moisture weakens the insulation and contributes to bearing corrosion.
Contamination
This results in: abrasion, corrosion and overheating. Small particles in the windings can gradually wear the insulation away as the wires flex during operation.
Electric motor failure is a large subject area with specialist knowledge required in a number of disciplines to enable a robust design to be made. We would welcome contributions from hobbyists, researchers and commercial organisations alike. Drop us a line at editor@glue-it.com