View Full Version : Best way to control 120 volt AC single phase motor

01-10-2005, 06:31 PM
Looking for something more along the lines of a schematic or "idea".

Not a light dimmer.

Any suggestions?


01-10-2005, 08:00 PM
Assuming you're talking about a normal AC inducition motor...I don't think you can. The speed is tied to the AC frequency, and if you mess with the AC frequency to any significant degree the starting circuit most likely won't work correctly.

3-phase motors don't have this problem because they don't need the starting circuit.

J Tiers
01-10-2005, 10:27 PM
Correct. Although you MIGHT be able to adjust about 20% down and maybe double speed max.

Figure a 2:1 with 80% of normal as the minimum.

I wouldn't mess with it.

If you have a shaded pole motor, or a fan type capacitor run motor, with no switch, you can do more with it. Shaded pole can be controlled by voltage fairly well, if they have a load like a fan on them. Otherwise they are kinda wild. They pretty much need a load steeply increasing with speed to be stable.