What kid of motor is this?

sounds like some sort of synchronous motor.

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snipped-for-privacy@whidbey.com wrote in news: snipped-for-privacy@4ax.com:

That single loop copper wire generates magnetic phase shift for rotation. The rotor should not be magnetized.

Massoud

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I had a record turntable that had a motor like that. The motor was synchronous and there was a shading pole to start it turning, and in the right direction. I think that was my old Empire Scientific turntable - the motor was in a perforated shielded cage and ran very hot.

** Modern washer pump motors are real odd balls - see pic:

It's basically an induction motor with a permanent magnet rotor. The rotor is inside a water proof housing ( black plastic in this pic) and drives an impellor pump via a rubber belt.

This construction means the winding is completely external and safe from water.

Due to inherent asymmetry, they vibrate a fair bit too.

... Phil

Have one like that in our Kitchen-Aid (Whirlpool) dishwasher. I believe it runs whatever direction it starts in. The impeller is symmetrical so that d oesn't matter. On ours the brass insert in the impeller came loose on the s haft. Fortunately it was under an extended warranty. Depending on vendor th e price ran $35-$70, some made in USA and others China. (didn't have to pay it, just checked part number) BTW that permanent magnet is very powerful.

Seems there's a lot of confusion here. Is it the motor rotor that is magnetized, or does an induction rotor drive a magnet?

In many pumps (these days) the motor will turn a magnet which in turn will turn the pump impeller in a separate (non-magnetic) housing by pulling the impeller along with the spinning magnet. It does away with shaft seals in a direct coupling that will leak after a time.

An extension of the old laboratory magnetic stirrer: a "stir plate" has a motor driven magnet and in the beaker/flask/whatever a Teflon coated "stir bar" follows the magnet around.

Thanks All for your answers. I thought that shaded pole motors could not have a permanently magnetized rotor and I thought that synchronous motors needed at least two external power source energized windings to get them to start rotation in a given direction. But as it turns out a synchronous can be a shaded pole type. And it was the answers I got here that led me to that conclusion. But I should have come to the correct conclusion without help. That's because the shorted winding in a shaded pole motor is still a winding. And even though it is not connected to any external power source like the other winding is it is still energized the same way a standard shaded pole is and it has the same function. Thanks, Eric

Got a Dual turntable motor at my desk that's a hybrid like that. It looks like a plain (but overly built) shaded pole motor but with two windings- one on each side of the rotor. It also has a segmented permanent magnet mounted on the cast Al cage/rotor that I guess makes is run sync after speeding up. There is a spider shaped set of poles surrounding the permanent magnet part. Never seen a motor like this before, but I also don't deal with record players.

d

The magnetization might be irrelevant.

Usually induction motors are made of transformer-steel, which acts like sof t iron and won't preserve much magnetization.

Also, any magnetization of the rotor is always getting wiped out by the "sl ippage" as the rotor moves slower than an exact fraction of 60Hz (so not 18

00RPM, but 1750 or something.) The strongest part of the rotating magnetic field is always sweeping slowly along the rotor, and not staying in one pl ace.

But perhaps if the motor was turned off extremely suddenly, then it might s tay measurably magnetized?

Or maybe they made the rotor out of standard steel laminations, rather than transformer alloy. In that case it would become *extremely* magnetized. Probably it would draw an unusually large wattage, and the rotor get smoki ng hot during normal use. It's like an induction furnace heating up a ste el frying pan.

No capacitor? Or no centrifugal starter switch inside? If not, then the p osition of the pole-shading shorting rings will force it to only go CCW or CW.