The motor is a 1HP motor that is rated at 575V, and a rated FLA of 1.5A. The service Factor is 1.25, it is a type 3428M and a XPFC enclosure. The fuses are 3A type CC. The overload is external, and is set to the nameplate value of 1.5A. The highest amp rating I record is 1.45A, so it is withing the FLA.
1 of the motors on the machine see's drastically different temperatures than the other. The surface temp of one motor is 87 C, while the surface temp of the other motor is 71 C. The motor with the 87 C surface temp failed first, and was replaced, and now the other motor with the surface temperature of 71 C is beginning to fail.
I hate that all I have are surface temps, and I am pulling teeth trying to get better information to work from. The 66 C temperature rise is the manufacturers tested data. I have used the 460VAC version of this motor in the past with no problems. The 575V version was custom, and uses the same frame size and insulation. The manufacturers tested at rated load temperature rise for the 460VAC version is also 66 C.
What I am thinking has happened here is that the manufacturer built a custom 575VAC motor using the 460VAC design, used the same frame size and insulation class. They probably should have used class F insulation.
I'm trying to get the Megger testing done on the motor, but the motor is several hundred miles away. Trying to decide if I should have the motor rebuilt with the class F insulation, or just use a step down transformer to 460VAC and use the 1HP 460VAC motor I know works in this application...