Johnny B Good wrote:

On Fri, 16 Mar 2018 22:55:15 +0000, Andrew Gabriel wrote:

In article ,
Brian Reay writes:
On 13/03/2018 12:26, The Natural Philosopher wrote:
On 13/03/18 11:39, Brian Reay wrote:
On 12/03/18 11:39, Andy Burns wrote:
Andy Burns wrote:

That said I expect to be able to get at the turntable motor/gearbox
without going near the "active" end ... any other gotchas?

Oh, and how universal are the "so called" universal motors?


They tend to be the larger motors sometimes used in washing machines.
The motors used to drive turn tables in uwaves (and water pumps in
washing machines and dishwashers) are small, AC, motors.

I dont think so for washing machines and dishwasher. Fairly sure the
ones I have taken out were brushed.


Universal motors of the type I'm describing have brushes.

I don't recall seeing one in a dishwasher but I've not looked at many
so that isn't conclusive.

Main wash pump motors that I've seen in dishwashers are all 2-phase with
a run capacitor.

The waste pumps in dishwashers and washing machines are all shaded pole
motors.

Drum motors in washing machines are universal motors (i.e. with brushes)
when belt driven, and stepper motors (brushless) when direct drive. Drum
motors need good starting torque and a very wide speed range, which the
other motors above don't have.

I can still recall my parents' first washing machine, which predated any
sort of electronic motor control. I'm not sure what the motor was, but
it was single speed, single direction. It had a sodding great gearbox
attached with a handful of large solenoids around it to do the gear
changes. I can still clearly recall the loud bangs as the different
solenoids engaged to change the drum speed throughout the program. When
it was scrapped, I saved the mains solenoids and some other parts, which
got used in a few projects afterwards. They did tend to overheat, as the
washing machine was for 200V mains, and had been converted to 240V when
the mains voltage changed by fitting a large autotransformer inside the
case, which I hadn't kept because it was too heavy.

I can imagine the need for a 10A rated 240v supply which would require a
400VA auto transformer in this case (40v difference at 10A) which could
easily weigh some 16 to 20 Lbs. Just as you described, not a lightweight
item. :-)

My knowledge of transformer theory was never very clear, but why is it
not rated for the total output, which might well be something like 10A
at 200v, 2000VA?



I can understand why you didn't hang onto it since any future need to
adapt a 200v appliance to 240v mains would be extremely improbable. The
only potential use would be in a museum of domestic electrical
appliances. Did you ever consider donating it to any such museums?


--

Roger Hayter