View Full Version : Small useful electric motors

02-06-2010, 01:22 PM
I had to take the power brush for the vacuum cleaner apart to clean out all the debris that were making it bind. Inside was a small powerful electric motor that uses a toothed belt to run the brush. I'm fairly sure it's 110 volt.
It looks like it could have a lot of uses. I'm going to stop by the appliance repair shop and see what they have along the same lines.


02-06-2010, 05:24 PM
Dyson has a motor in certain models of their vacuums that spins to 100,000 rpm.

02-06-2010, 05:51 PM
Dyson has a motor in certain models of their vacuums that spins to 100,000 rpm.

Intriguing. What could an HSM guy use one of those for? My feeble brain can't think of a darn thing. :confused:

02-06-2010, 06:28 PM
The brush motor will be a permanent magnet motor that runs from rectified AC. The main vacuum motor is a series wound universal motor and will run on AC or DC. Series wound motors are capable of extremely high rpm with the limit set only by the load and internal parasitic losses. They have terrible low rpm performance and will cook if run too slow under load. The coils are normally very low resistance and the motor depends on back emf to regulate current draw.

02-06-2010, 07:25 PM

02-06-2010, 08:25 PM
Hmm. That is a brushless DC motor. Trouble with those is they are limited by the controller to what they can do. It probably doesn't have a variable speed control function and it would be a difficult task to design one without specific motor properties.

I think it is a good time to start stocking up on regular brushed permanent magnet motors.

02-06-2010, 09:47 PM
'no carbon brushes so no carbon emissions'- got a good laugh out of that.

Those brush head motors I've seen in two sizes- not sure what the larger one is rated at, but the smaller one, 2 1/2 inches long not including the shaft, and with the flat sides is rated at 30 watts, .38 amps draw, and 7800rpm. They do have the full wave rectifier built in, so you just feed it 110vac. I've used a few now for various purposes, the latest use being as a sander. I turned up an aluminum disc to mount to the shaft, about two inches in diameter, and glued a piece of zirconia sandpaper to it. Obviously you can't bear down on it too much, but I've used it to grind on all kinds of things. So far the zirconia hasn't done any more than discolor slightly- it doesn't seem to be wearing out.

I have a couple of the larger motors, the round can ones. I also have a miniature skil type saw- not sure what that was all about initially, but I plan to put one of those motors on it and make it work. Don't recall now, but I think it takes a 3 inch blade. This might end up just being for laughs.

As far as the brushless motors, I've got an idea floating around in my 'design committee' for a sort of universal commutation circuit, which could be used for pretty much any three phase pm motor. This circuit would be able to drive a very small motor directly, or it could give the drive signals to power transistors for larger motors.