Re: [CAD_CAM_EDM_DRO] VSD QUESTION

Bob Muse wrote:

>Hi John
>
>If your router has brushes, it is most likely a "universal motor". This
>may be operated on AC or DC. One easy way to control the speed is just by
>controlling the input voltage with a variac. There may be other controllers
>designed to do this job also--but the three phase VFD is not a good choice.
>
>

Yup, listen to Bob, he's right. But, there's another reason! The 240 V VFD
rectifies the AC input, to get about 340 V DC on its capacitor bank. It
then
switches this voltage on and off at a high rate to get an average that looks
like the desired AC output waveform. So, no matter what voltage it is
supposed
to be putting out, it is manufactured out of 340 V pulses! I don't think
a universal motor is going to like that AT ALL!

Jon