Tuesday, June 23, 2009

[Electric Boats] Re: dumb question about a fan



Thanks, Matthew. I didn't know that most household electric motors were induction motors.

md

--- In electricboats@yahoogroups.com, Matthew Geier <matthew@...> wrote:
>
> constancedraper wrote:
> > So, I am assuming this motor was generating some amount of electricity. What would it take to capture that? Something more complicated than a diode?
> >
> A standard domestic fan motor is likely to be an induction motor, they
> don't make good generators, there are no magnets in there, the motor has
> to be supplied with power to generate the magnetic fields.
> 3 phase induction in larger applications can and do 'regenerate', but
> they also have reasonably complex control systems as well, they don't
> just hook the motor straight to a resistor (dynamic braking) or a
> battery. Some of the 'brush-less' motor/controller combos being used on
> our boats are capable of regeneration, the argument is over whether it's
> worth the returns, not the tech. The tech works.
>
>
> My electrical theory isn't up to being able to conceive how you could
> get a single phase shaded pole induction motor to 'regenerate'. It
> certainly won't on it's own, no magnetic fields, but I'm not clear if
> you could 'excite' the system to start making electricity and self
> sustaining those all important magnetic fields. Unlike a series motor
> with field coils, there isn't a separate set of coils you could energise
> to make the fields. Induction motors are black magic. :-) (But cheap,
> simple and relatively efficient, hence popular for things like fans and
> other mains powered domestic appliances that need a motor).
>

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