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Posted to sci.electronics.repair,free.uk.diy.home,uk.d-i-y
Andrew Gabriel
 
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Default Safely discharging a capacitor

In article dsiqf.694$2B5.463@trnddc01,
James Sweet writes:
Why do you say that? Most European washing machines use series wound
universal motors with carbon brushes. I've got a Creda washer sitting in
my basement right now awaiting arrival of a set of brushes amoung other
things, no idea how it ended up on this side of the pond but it's a cool
little machine.


A European washing machine operates its motor at a large
number of different speeds (and even gradually vary the
speed in some cases) throughout various stages of the
wash cycle, and depending on the wash program selected.
This is most easily done with a universal motor combined
with an electronic speed control board and servo feedback.
(It used to be done with an induction motor and solenoid
operated gearbox 40 years ago, but that's more expensive
and a lot less flexible.)

Tumble driers only have to be able to reverse the drum,
but don't need to change the speed. For this simpler
requirement, an induction motor tends to win.

--
Andrew Gabriel