High Voltage Motor Temperature Rise

Greetings to all,

A high voltage motor was sent for rewinding, and when it came back, its temperature increased by around 20 deg. It is cooled by an air-to-air heat exchanger and motor cooling fan (MCF) driven by motor shaft.

Can someone help in identifying the possible causes of temperature increase?

I assume that the heat exchanger is most probably causing the temperature rise, but how to check that?

Is it possible that the winding insulation affect motor temperature? I mean for two motors exactly the same, if we used different winding for each one, i.e. class F for one and class H for the other, would that affect the motor temperature?

Thank You in Advance
Have you asked yourself:
1. Has the heat exchanger changed in any way during rewind
2. Has the motor cooling fan changed

If neither, then it's possible the copper in the rewind is not as conductive/not creating the same magnetic field as the original.
That is a little odd you would notice difference in temperature without having other concerns such as current draw which would affect temps. Ambient temp, load, voltage variation, current, fan pitch, intake obstruction, and other things as well can effect temps. Question is, are the temps within reasonable acceptable limits. I have no experience with a motor cooled by a heat exchanger, what type of system is this?


what temperature do you measure exactly, copper or iron or insulation or air ambient, and where? It is possible the the old sensors were different of placed in a different way with different thermal impedance, so you get another value of temperature.