Motor Surface Temps

You should determine the relationship between outer and inner temperatures.

procedure:

-measure coil resistance with cold and hot motor and the environmental temperature

First measurement with the motor stopped long enough to have same temperature in the coil as outside, second after a time under load long enough to reach end temperature.

With resistance measurements one can determine temperature of coil and knowing outside temp the thermal resistance between coil and exterior can be computed. After this only by a measurement as did you can know with good accuracy how hot is in average the coil.

The temperatures refer to the coil winding temperatures and not at surface whenever NEMA class of insulation is stated.

For Class F the allowed rise of temperature over the ambient of 40 deg C is 115 deg.

That is 155 deg C is the max allowable temp ( 40 deg ambient + 115 deg allowed rise)

Surface temperature is always lesser than coil temperatures.

Looking at the max of 128 deg C you appear to be in the safe zone although I will advise to check the temp of coil/windings rather than outside body temperature to be absolutely safe!

If you are so much worried about the motor safety, next time order the motor with thermisters that would take care of safety with respect to temperature regardless of the reason of temp rise.

Trust this helps.

Regards

Chuck Cowlagi