sccjr, it was 60hz. Good thought, because if you apply too low a frequency, (or if the motor was designed for a signifigantly higheer frequency) it doesn't create enough impedance to limit the current flow, so there is some validity to that. IDK how far off the rating would have to be to cause a problem, but I dont think the delta from 50 hz to 60 hz would be much of an issue, but Id have to look that up. Aircraft usually use 400 hz transformers, and motors, because due to the greater reactance at the higher frequency, they convert more efficiently, so they can be made smaller and lighter than 60 hz X-frmrs. It was said to me many years ago in aircraft school, if you put 120 vac, 60 hz, onto the primary of a 120vac, 400 hz aircraft transformer, you will draw massive current. (understatement!)

Which makes me wonder, when powering a 60 hz AC motor with a VVVF drive, what limits the current flow at lower frequencies, when the motor is turning slowly? I imagine the currrent sensing coils around the three phase feeders tell the drive board to chop the sine wave earlier and earlier, resulting in less RMS voltage accross what is essentially lower peaks.