# DC Motor operating temperature??



## Randeb56 (Apr 6, 2015)

Just wondering if someone can tell me what would be a normal operating temperature temperature range for a brushed 72v DC motor. Just roughly. Thinking of having my blower put on a temperature sensor to turn it off and on as needed.


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## major (Apr 4, 2008)

Randeb56 said:


> Just wondering if someone can tell me what would be a normal operating temperature temperature range for a brushed 72v DC motor. Just roughly. Thinking of having my blower put on a temperature sensor to turn it off and on as needed.


Most motors used in EV conversions are class H. Insulation good to 180ºC. Typically that will relate to about 90-100ºC on the outside of the frame or ~130ºC on the outside of the field coil (inside the frame). Of course the motor is massive so there is a time lag between the hot spot (usually the armature or brush) and the placement of a sensor. 

Those are limits. Normal operation is on the order of 120ºC on the copper windings, average.


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## Randeb56 (Apr 6, 2015)

Excellent response Major. Thank you for the clear and concise answer I will put it to good use.


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## browncamaroz28 (May 14, 2014)

What would be safe operating temps for the brushes and armature? I was intending on using an infrared temp sensor pointed on the commutator on my adc9 and I know evwest unofficially said 240 in this video at minute 3. https://www.youtube.com/watch?v=SVkJjt_Peg0 I take it that was Fahrenheit. 

Thoughts?


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## major (Apr 4, 2008)

browncamaroz28 said:


> What would be safe operating temps for the brushes and armature? I was intending on using an infrared temp sensor pointed on the commutator on my adc9 and I know evwest unofficially said 240 in this video at minute 3. https://www.youtube.com/watch?v=SVkJjt_Peg0 I take it that was Fahrenheit.
> 
> Thoughts?


I see no reason for not using 180ºC for a class H motor as a limit. Often techs in the lab use an assumed 15º hot spot so call the limit at 165 measured.


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## browncamaroz28 (May 14, 2014)

Wow that's higher than I expected! I'll probably kick the blower on earlier and de-rate the throttle depending on how quickly the temp increases. Thanks for the responses, I'll quit hi-jacking this thread now


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