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wrote:

Is there any way to use a VFD to control the speed of a single (1)
phase motor?

thanks,
joyful

I can't answer about what's actually done in practice, but in theory,
yes you could. There are a number of difficulties, even in theory, to
doing this, however.

The biggest problem would be starting, where you would need to drive
both the run coil and the start coil with the correct phasing (a single
phase motor with it's start coil is really a ******* two-phase motor).
The second biggest problem would be running smoothly at slow speeds
without overheating, which also involves driving the run and start coil
correctly. Because every model of motor has a different way of treating
start coils, making a universal VFD would be a big pain.

But a 3 phase motor has dead standard behavior, so a 3 phase VFD doesn't
need to be matched to a given model and brand of motor -- it can just go
by voltage and current rating (or voltage and horsepower).

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

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