Published On Jul 11, 2015
The sound made my an electric motor powered by a variable frequency drive can be reduced or eliminated by changing the carrier frequency (chopping frequency) of the signal.
The VFD is an Hitachi L200 powering a Pratt & Whitney Model C lathe. The motor is an early 1950s Westinghouse 220/440 volt 3 phase 3 hp unit built on the obsolete 225 frame.
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