On Sep 29, 12:47*am, David Lesher wrote:
Vernon writes:
Joseph,
I'm still trying to wrap my electrically challenged brain around the
differences / advantages / disadvantages between rotary converters and
VFDs. *As soon as I'm able to articulate an intelligent question I'll
ask one!

A VFD is a big magic solid state box that delivers AC of from {say} 10Hz
to 100Hz. It USUALLY will be one able to deliver 3 phase power. [But
there may well be smaller single phase ones, so cabbage emperor...]

How it does that.... Well think of it as an audio oscillator and a
BIG amplifier for the speakers err motor.

Its major plus is the variable frequency means whatever motor it feeds
will be variable speed. It's almost a waste to buy one just for a single
speed task, but a friend did to drive an air compressor.

A rotary converter is a semi-kludgey way of getting 3 phase from a single
speed source, at the line freq. [60 Hz]. Ditto the capacitor-based
schemes. *They may work well enough for your case. But neither one will
deliver the large starting torque a true 3ph supply will offer.

Does this help?
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Hi David,

It does help. But I don't understand this part:

"They may work well enough for your case. But neither one will
deliver the large starting torque a true 3ph supply will offer."

Are you saying that a VFD is "a true 3ph supply..."? Or are you saying
that "nothing's as good as having 3 phase and not NEEDING a box"?

V