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When it comes to motors, how hot is hot?

Plant Engineering
Publication date: 
September 2013
Jim Bryan, EASA Technical Support Specialist

It's not uncommon for a maintenance technician to call a service center about a repaired motor that’s now “running hot.” When asked how hot, the reply frequently is: “Well, I can’t hold my hand on it!” Think about that answer for a minute. The typical human can tolerate touching something that’s about 60° to 65°C (140° to 150°F), depending on calluses, threshold of pain, or how many people are watching. This article goes on to examine how hot is too hot for the motor winding. Temperature control is an important factor in successful motor operation. Care must be taken in the design, application and maintenance of these machines to optimize their performance and life.