Four reasons why electric motors overheat

Increases in the temperature of an electric motor reduce its lifespan. By knowing the reason why electric motors overheat, users can develop a preventive maintenance strategy to combat inefficiencies.

By David Manney, L&S Electric November 3, 2017
Many problems occur with electric motors. Including those associated with lubrication and voltage spikes. Also, over time, excessive heat occurs. Increases in the temperature of an electric motor reduce its lifespan. The winding insulation deteriorates, and the bearings may also deteriorate.

Why Motors Overheat

There are many reasons electric motors overheat. There are four primary reasons why overheating occurs:

1. Overload

The standard current tests most load levels, but overvoltage may still be an issue. Reducing the current may not entirely reduce excessive heat. It is best to know the operating capacity of your motors. Maintaining that level helps keep excessive heat to a minimum.

2. Starting and stopping

Limiting how often the motor starts and stops reduce its heat. Keep a close eye on the number of times it starts. If necessary, cut it down. Online motor testing is the easiest way to monitor the starting and stopping of the machine.

3. Poor power conditions

Power conditions often result in overheating. Poor power is associated with the use of VFDs, although the VFD may not be the primary cause of the problem.

4. Operating conditions

Operating electric motors in poor environmental conditions also leads to excessive heat. Associated problems include clogged ducts and high ambient temperature.

How to help motors keep their cool

One way to keep your motors cool is by reducing the excessive load that the motor handles. When considering the specifications of the task involved, match the appropriate motor to the necessary load.


Testing the motor as part of a routine maintenance program also reduces the possibility of failure due to excessive heat. Don’t judge the temperature of the motor just by feeling the outside surface with your hand. Touch, in general isn’t an excellent sensor; what feels hot to you is cool for somebody else.

Maintenance programs

That isn’t to say don’t worry about how hot the motor feels. Use the appropriate testing methods to find hot spots within the motor windings. Those accessive hot spots reduce the motor’s lifespan.
Ensure that your motors have the proper protection in place. That protection includes thermostats and overload protectors. One piece of a good maintenance plan, these devices ensure that the motor is not operating at damaging temperatures.

Electrical motors are often some of the most expensive assets in your facility. With proper maintenance and common sense, extending their useful lifespan becomes a little easier.

David Manney is marketing administrator at L&S Electric. This article originally appeared on Watts New, L&S Electric’s blog. L&S Electric is a CFE Media content partner.

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