On 03/04/2012 01:36, Arfa Daily wrote:

I don't think that in 35 years of owning washing machines, I have ever
had one with anything other than a "universal" (as in field coils and
armature in series) brush-geared motor fitted for drum drive. Mostly the
pump motors are brushless induction motors, and certainly, all of the
tumble dryers that I have owned have had induction motor drive.

Bear in mind that in the UK, unlike in the U.S. , we went straight from
twin-tub machines, with a vertical actuator in a static tub, and a
vertical spin dryer, to front loading 'automatics'. Very considerable
oomph is needed to shift a horizontal rotating drum full of water and
washing, and even more to get it up to 1000 RPM and beyond, for spin
drying. I'm not sure that a compact induction motor would have the power
and revs range to be able to do that. Not so easy to control the
rotation direction either for the anti-tangle reversing washing action.
At least I have always assumed that was the reason that brush-geared
motors were used in these machines ??

Arfa

Hi Arfa

I spent over 20 years repairing domestic appliances. You are right about
the twintub/front loader thing. A couple of manufacturers made top
loaders, Hotpoint, which was a huge machine used a very complicated
gearbox and centrifugal clutch arrangement - when the motor ran in one
direction it agitated the washing, and circulated the water, and in the
other direction spun the drum and drained out. All relatively trouble free.

Philips made a compact top loader with a low voltage DC motor (using the
heating element as a dropper resistor) and a silly bakelite centrifugal
clutch and variable cone drive. The drum was similar to a front loader
but mounted sideways with a hatch in the periphery.

Most if not all British front loaders used brushed motors, continental
machines generally used induction motors using capacitor control.
A couple of exceptions were Indesit and Zanussi which used brushed
motors in their high spin speed machines, I think about 800 rpm was
about the limit with an induction motor.

The few Brit machines which used induction motors - Hotpoint twintub and
top loader - used a 'relay' in series with the field coil to momentarily
energise the starting windings. If the relay stuck the magic smoke was
released!

I have no idea how many pairs of Hotpoint/Hoover/Servis/ motor brushes
I`ve changed, but it must be many many hundreds.

You can readily get service manuals for all Hotpoint machines btw.

Ron