Overheating Electric Motors

As a general rule of thumb, operating a motor more than 10°C above the motor’s rated insulation class may decrease the life by half.  Excessive heat will accelerate the degradation of a motor’s insulation system.  Heating of a motor can be caused by overloading, too frequent starts, high ambient temperature, to name a few. For example, a motor with a class F insulation system is rated for 155°C. If the motor exceeds this temperature more that 10°C then the life of the insulation system may be cut in half.

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