Hi all,

I finally got around to taking a look at our tumble dryer, which has been
out of action for a while (SWMBO's nagging finally paid off for her). In
order to get it spinning round, you have to give the drum an initial
shove, after which it rotates totally fine. But it cannot revolve without
that artificial boost at start-up.
I don't deal with repairing this kind of gear, but still fixed it within
5 minutes anyway. The 7uF/400V cap that lies strapped to the motor was
faulty (had gone completely open-circuit). It was the first thing I
checked.
Nevertheless, I'm still unsure what exactly this cap's purpose is. AIR,
they are often referred to as 'motor-start caps' or 'motor-run caps' but
why are they needed? I'm guessing if they weren't used then manufacturers
would have to fit more powerful motors simply to overcome the start-up
inertia and a cap is cheaper than a heftier motor. But that's just a
guess. Can some kind soul disabuse me of my ignorance here, please?