On Thu, 27 Oct 2016 12:15:18 -0500, Jon Elson
wrote:

There was a discussion a LONG time ago about a washing machine pump motor.
I have a Kenmore Oasis washing machine that I've had to do some repairs on.
The drain pump has gotten clogged a few times (coins, nylons) and I've been
able to remove the clog and get it going again. I posted a partial
description of the motor, because I couldn't quite understand it.
Now that the pump has finally gone to complete failure, I was able to
investigate further.

So, it has a stator quite similar to a "phonograph motor" although there are
no shaded poles, as I had expected. The rotor is a 2-pole ceramic magnet.
The rotor runs in water, so there are really no seals required in the pump.

When digging in deeper, I found there is a slip coupling between the motor
rotor and the pump impeller, that allows the rotor to make almost one
complete rotation before it grabs the impeller. I suspect this is to allow
the rotor to vibrate wildly until it gets into sync with the mains
frequency. AHH, and the pump is clearly designed to run in either
direction! Now, it is all starting to make sense. The pump does make a
rattling noise before it starts. Kind of ingenious design, probably had to
make a BUNCH of prototypes before they got it to reliably start spinning.

Anyway, the pump bearings (water lubricated) are massively worn, and the
rotor eventually wore through the plastic housing.

Jon
Greetings Jon,
Thanks for the motor update. I have been thinking about that motor and
why they would use it and it must be because shaded pole motors are so
inefficient.
Eric