[joprinz]

I was trying to find what motors i can obtain locally. A friend of mine gave me an old motor and told me if I could make it run he has plenty of motors of the same type. But I had never seen a motor like this before. He said its from the blower of an old air conditioning unit. There was some circuitry near the place the wires come out of the motor (probably hall effect sensor or the like) which is not there anymore.

It does not have any brushes.I checked the coils. They are intact. A 12v dc can make the motor spin one step. Switch the battery poles n we got it make another step. Is this a Stepper motor? or a Brushless DC/AC motor? Or any toher type? Has anyone come across a motor like this?

Hope someone can help me identify what kind of motor it is!

Also I was wondering if this motor can be used in anyway as drive motors for CNC?

Thank You!

Joe!

[Al_The_Man]

It looks like it might be a ECM (Electronically Commutated Motor) now used on furnace and A/C fans.
It is similar to a BLDC motor, but much cruder, I don't think it will be practical to use in a servo application, especially without the electronics attached to it.
Al.

[joprinz]

Thanks Al. Do you know any good reading material on ECMs? Eventhough this motor is probably useless as a drive motor but I'm curious as to how the motor is driven. I did a google but couldnt find anything detailed. But I did read about GE's furnace ECM's which got me all the more curious to learn

Joe!
I'm already strugglin with serious lack of time in my life n yet things like these somehow make me wanna loose more sleep...ha! Learning new things is addictive too I guess... God Help me

[Al_The_Man]

I don't have a link to any reference for ECM, I assume GE keeps the technical side proprietary, but the motor is basically a three phase motor with a P.M. rotor, there is usually 3 feedback devices triggered off the rotor to indicate relative position of the rotor to the stator, one for each phase and the motor is commutated electronically as a variable frequency three phase motor, if you read up on the more sophisticated BLDC and especially AC synchronous servo motor, this should give you some in depth info.
Al.

[joprinz]

Thanks Al. I'l look for more info on BLDC n AC synchronous servo motor. Thank you for the info

Joe!

[RomanLini]

Sorry to contradict Al, but it seems to be a 2-phase motor.

These old 2 phase brushless motor are normally "dumb" they don't have any sensors. They were sometimes used for fan motors at a fixed AC frequency, and used just a capacitor to cause the phase shift for the second phase with the first phase driven direct from the AC. But like you said it may have had a hall sensor for the phase switching and run from DC.

Now without the sensor it's basically a bipolar stepper motor that makes 4 steps per rotation. And useful for a fan, but probably not much else.

[joprinz]

Well a two phase motor is required to have 2 sets of coils right??? this one only has Two wires coming out. The only thing we can do to make it run is keep changing the polarity. It does move in steps when you change polarity but its crude at best to produce reliable spinning of the motor with that method. Sometimes it just stands n vibrates. The Hall sensor was probably there to assist the pulse timing.

Joe!

[Al_The_Man]

Yes, a 2 phase, or more correctly, split phase requires at least 3 wires, two sets of windings.
Also these would typically have an induction style rotor, the fact it has a P.M. rotor, indicates it would have external commutation of some kind.
Al.