The motor is the problem. Chances are it is not a high quality motor and
this means the windings and laminations are not supported by resin
impregnation as well as they could be. Even a high quality motor will make
some noise, but it will be more of a hiss than a whine depending on the
enclosure type and pwm freq.

Randy

"Steve Smith" wrote in message
...
I have two different VFD's. Both turn a motor (different motors) just
fine. One is completely silent (TECO), the other one makes a noticeable
and irritating whine (actually the motor makes the noise). The noise is
coming from the PWM in the drive.

I haven't tried every PWM frequency, but I have tried about a dozen.
They all whine until I get up to 16kHz, where I don't hear it. This
would be fine except that above 12kHz the drive is only rated at 80%
(2.4HP); I intended to run a 3HP motor with it.

The noisy VFD is a 3HP Cutler Hammer that I just bought. I have it set
up for test with 4' of Romex connecting between the VFD and a 3HP
motor. The motor is grounded to the VFD and has no load.

I would appreciate suggestions on how to quiet the drive but keep the
PWM frequency at 12kHz or below. Will a load change things? Will a
different motor change things?

Thanks,
Steve Smith