I just realized that I overlooked something: I think the motor is a red herring. It's the VFD that will determine performance. The frequency and the voltage the motor operates on will be determined by the VFD. If the air compressor, VFD and motor come as a set, the manufacturer could have designed it to operate at a different performance than the nameplate on the motor indicates.
Some motors as small as 4Hp are designed for both 400V and 690V operation. It wouldn't suprise me if this huge 75Hp motor is too. If I'm not mistaken, this in combination with a VFD would allow use with higher frequency and voltage and hence higher power than the nameplate indicates.
I'm no expert in motors, and I hope someone will correct me if I've written something stupid.
[This message has been edited by C-H (edited 03-17-2003).]
