Re: AC single phase motor speed control

The general electric rapsheet on their AC motor product line(s) indicates that variations beyond +/-5-10% of voltage and/or voltage oscillation
frequency will cause the motor to function "with reduced efficiency," in terms of rotational speed, torque generated, wear to insulation, and thermally (or, in the case of increase of those values, just thermally and insulation [-ally?], oh yes, and slip increases, which is what causes the two previous issues ). They mention that a 25% reduction in voltage results in around a 50% reduction in torque (actually it's a table, that's one of the values I remember)and about a 40% reduction in motor speed, but generates significant heat (conservation of energy, of course) and potentially can result in wearing out winding insulation.
It does seem like using mechanical power transmission of some sort would be less likely to kill the motor, but I have certainly learned a WHOLE lot about the AC induction motor. I never did make it to BurningMan. But it's been a fun trip just the same.
Someone pointed out to me that the capacitor start motors (which both of the functional AC motors I have happen to be) use centrifugal switches which will cause the motor to go into a high-torque "start mode" if the motor slows, which sort of defeats the purpose (this is mentioned in the GE docs, but not as any kind of a specific problem - just that the specific motor in question uses a capacitor during startup and runs on induction once it's going fast enough to open the switch - no mention at what speed the switch disengages). Apparently running the motor in such a "start mode" too much will kill the motor more or less immediately.
Ahhhnhhh well.
Thanks to everyone who contributed suggestions (unilaterally - "use a DC motor" - variations from car starter motor to volkswagon generator from a pre-1970 super-beetle/fastback) .
At this point, I'm not in a hurry about it anymore. So I'm going to do the right thing and get a DC motor for the purpose.
Again thanks to everyone who gave The Suggestion, which I of course stubbornly ignored for as long as I was able.
DJ

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