[avr-chat] OT: Motor vibration due to PWM harmful?

[Erik Christiansen]

While fooling with FET drive for a 200 watt DC motor, there was a fair
howl emanating from the motor when the PWM frequency passed through
mechanical resonances. I've read of ruined bearings in large motors, due
to arcing through the lubricant, due to voltage build-up on the rotor,
apparently exacerbated by peaky drive, but the wear effects of
continuous high frequency mechanical vibration doesn't seem to be
mentioned much.

OK, I could keep the frequency fixed, and above 20 kHz, but that only
minimises the vibration.

Filtering the drive's output would silence the motor, but would
longevity be noticeably improved, I wonder? (Any anecdotes would be most
informative. :-)

Erik