Awl --

How to do?

TRIACs? http://en.wikipedia.org/wiki/TRIAC
In that article they mention "alternistor". Useful? Never heard of it.

How bout PWM? http://en.wikipedia.org/wiki/Pulse-width_modulation good
article, overview, incl. rheostats and variacs. Not clear, tho, if pwm acts
to change the effective input frequency.

I'm guessing that, in general, speed control of 1 ph induction motors is
not so swift, given that people here are swapping out 1 ph induction for 3ph
+ VFDs.

But if it IS doable on smaller motors, it would be a big help.
The blower motor at hand (kitchen hood) is surely no more than 2-3 A, and
I'll bet about 1.5 . I've used a variac on this motor, with very middling
results.

If 1 ph induction is freq dependent, why can't a VFD be used on a 1 ph (220
V) induction motor?

If I need to go 3ph+VFD, Dealerselectric.com has fractional hp 3 ph motors,
down to 1/4 hp, prices not on web.
Graingers has no 3 ph motors under 1 hp, and none of those under $250...
wow....

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EA, PV'd