Identifying type of AC motor


I want to control the speed of a floor fan I have at my shop. I’ve done some reading and learned that I need to find out which particular type of AC fan it is. Does anyone know of any resources to figure this out?

Here are the fan’s specs:

model TPI CF-20
3-speed, 1/5HP, permanently lubricated, sleeve bearing,
Rotary 7’ long - SJT type 3 conductor Aluminum Coated, steel with retaining clips
185W, 1.65 A

It seems like people generally id fans using the specs and/or the use of the device. Are there any visual indicators? (I’d like to avoid taking the thing apart if possible, but for future readers perhaps that info would be useful too)

I’ve been reading about diac/triac circuits, random-fire SSR’s. The following beast of a thread has a lot of good info, but just a lot of info in general and things get kind of muddy at times.

Some other info about my purposes - I want my fan to go from normal operating speed down to, say 80 rpm. Below 60 rpm would be sexy as hell. But I know that depends a lot on the motor type and how I’m controlling it. I want to use an arduino to pwm-control in the end. I will be using the motor for its original purpose - to control the fan.

thanks a lot,

Sorry I cant be of more help here, that link is to an article by a local magazine in Australia, they sell those units as a kit, maybe buy one and play with it? I am used to hearing about Filament based light dimming circuits, im not sure if these would work on an AC motor.

it is probably an induction motor which means you would need a VFD (variable frequency drive) to control it.

If it's singly fed, its most likely an induction motor. If it is doubly fed (highly unlikely), it's a synchronous motor.

HTH -Igor