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Posted by Roger_Nickel on March 17, 2006, 3:58 pm
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Alex wrote:
> My 3 phase motor(connected to VFD) makes high pitch sound when stopped.
> The sound is not loud but audible and it's geting on my nerves.
> Motor runs fine.
>
> Is it suppose to be this way or there is something wrong with my setup?
>
> Motor AC 3 phase 240V Leeson 2HP
> VFD - KB Electronics - KBAC-27D
> http://www.kbelectronics.com/data_sheets/9481.pdf
>
> Thanks,
> Alex
>
The VFD sinewaves will be built up by modulating the polarity and
duty cycle of a high frequency square wave. Depends on the
controller but even with the motor stopped the windings are
probably energised at a low level to keep control of the rotor.
Every switching cycle of the drive waveform involves losses so
it's a trade off between audible noise and switching losses when
choosing the drive frequency. The noise is probably
magnetostriction in the motor laminations which is drowned out
when the motor is running at speed. Don't worry about it unless
something else is obviously wrong. You could get a newer drive but
it will probably drive your cats crazy.
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> The sound is not loud but audible and it's geting on my nerves.
> Motor runs fine.
>
> Is it suppose to be this way or there is something wrong with my setup?
>
> Motor AC 3 phase 240V Leeson 2HP
> VFD - KB Electronics - KBAC-27D
> http://www.kbelectronics.com/data_sheets/9481.pdf
>
> Thanks,
> Alex
>