Quick ? for EE's.
 

I have what appears to be an induction motor on a 12" squirl cage fan that I use for ventilating an enclosed patio during the summer months. Even being a SC fan, it's kinda noisy, so I thought I might throttle it down with a controller. What shoudl I look for beyond a silly dimmer switch? Will a router speed control (for a brush type motor) do the same job? It's not hard wired, so an inline device would be ducky.

TIA

Induction motors are AC synchronous motors, which means their RPM is dependent on the power line frequency. There's no easy way to vary their RPM, and a dimmer switch won't work. You can chop the AC voltage somewhat and get a slight RPM reduction, but a little too much it will just stall. If it's belt driven you're best bet is to go to a larger pulley on the squirrel cage, or smaller on the motor shaft. If the cage is directly mounted on the motor shaft then you're SOL.

Sorry, forgot to mention it was direct drive.

Anyway, that was the answer I was looking for. I'll mount it further away and use ducting or buy a smaller fan. Last year, I used a thermostat controlled 16" attic fan. That sucker was pretty noisy too being a blade type. I ought to just get a cheap stove hood ;)