Why electric motors fail in industrial applications and how to prevent it

Why electric motors fail in industrial applications and how to prevent it

With their high reliability, we sometimes forget why electric motors fail and how avoiding this needs some simple TLC. Focussing on this important issue, ABB has an interactive online booklet examining the main reasons why electric motors fail and how to prevent it.

They also identify the six main failure categories, and of these, bearing failure accounts for over half (51%). Helpfully, each category is further broken down by principle cause, along with suggested preventative actions.

In general, motor failure is not due to age or operating hours alone, but to one of the main categories.  ABB identifies these along with examples of suggested actions. Although the focus is on ABB motors, most comments apply to industrial electric motors: if in doubt, read the manual.

Why electric motors fail

Why electric motors fail in industrial applications and how to prevent it


51% Bearing failures

Reason Suggested actions
Insufficient greasing. Re-greaseable bearings need regular maintenance every 2000 hours or three months
Excessive greasing Incorrect greasing procedure may damage seals
Incorrect lubricant Due to incorrect lubricant or mixing of greases
Misalignment Due to incorrect alignment of motor and load-many causes
Shaft overload Indicated by excess wear and also usage of drive belts
Vibration Chiefly problems with shaft or housing vibration
Overheating Ensure correct grease for high temperature applications


16% Stator winding failure

Overheating Resulting from excessive-visually inspect windings
Overloading Consider thermistor protection


16% External environmental conditions

Motor operating temperature Regularly checks of cooling system
Humidity and environment Corrosion from excessive ambient temperature/humidity and moisture
Contamination Due to foreign particles or wrong IP
High ambient Motor not derated for high temperature


5% Rotor bar

Excessive starting frequency Leading to thermal stress or inertial fractures
Overloads Locked rotor or stall conditions
Undervoltage Low voltage use increases running current


2% Shaft coupling

Misalignment Frequently due to incorrect mounting. Use laser alignment
Poor installation Alignment of incorrect choice of coupling


The remaining 10% of failures are due to a combination of the above, operational misuse, lack of experience or vandalism.

The appropriate use of ABB variable speed drives can mitigate many of these problems as they also operate as a protective device as well as their soft-start capability.

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