On 28/10/2016 21:18, wrote:
On Friday, October 28, 2016 at 3:23:18 AM UTC-4, N_Cook wrote:
On 27/10/2016 18:15, 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


So like a smaller version of a central heating circulation pump,
magneticc oupling through a membrane. At least washing m/c get used
through the summer , so nver a chance to seize up

I have used TACO and Grundfos sealed hydonic circulator pumps - our present system uses two TACO systems and one Bell & Gossett 1/4-horse as it is a summer-winter system that makes domestic hot water as well. The TACO pumps have one (1) moving part installed as a cartridge, and behave as does any other AC induction motor designed without brushes. There is no 'magnetic coupling' in the true sense of the word, as there is only that single moving part. I would agree on the 'synchronous' description as the impetus has to comes from somewhere.

The Bell and Gossett, on the other hand has the standard induction motor using a spring-coupling to a separate pump housing with a sealed bearing. Much larger, much heavier, and much more powerful. That is what moves the approximately 110 gallons (400 liters) of water through the 34 radiators on a 2-pipe system, that includes just under 450 feet (146 meters) of pipe in total. The house was built in 1890, and substantially expanded in 1928, when the hydronic system was first installed. It is a 2-pipe, 3-zone system designed for gravity supply and return, with a single circulator not added until the 1950s. We converted from oil to gas and added the indirect water heater, that conversion requiring the two additional circulators. But the first Grundfos pump I installed about 38 years ago is still going strong. And my first TACO pump (27 years) is equally good, so far. I have rebuilt our B&G twice - the first time just the coupling - the second time, the support bearings and coupling.
I should have done the support bearings the first time. That, now, has 8 years on it, but is dated 1978 as the original install-date.

https://www.youtube.com/watch?v=E0X8m0BGZ1g

Peter Wieck
Melrose Park, PA


A problem with synchronous motors, is they can start backwards unless
there is a "kicker" mechanism