On Mar 8, 9:24*pm, "Existential Angst" wrote:
Awl --

So I'm amassing a collection of perm. mag. DC motors for my various
(de)generative follies, but a friend said he took apart a gas powered
generator, and observed no magnets, with both stator and rotor being
wound -- suggesting that AC induction motors should provide juice, but mine
don't.

Was my friend wrong, or can wound rotors/stators yield juice, and if so,
under what conditions?

How are back-up generators generally wound, as well as prime generators,
such as coal, hydro, etc?

Will a typical 3 ph motor throw out juice, if driven by a pony motor?

Any primers on this stuff?
--
EA

A old-style non-PM DC generator usually relies on residual magnetism
in the pole pieces to start the cycle. One of the to-do items after
working on a VW generator was to connect the battery to the field
windings the correct way round in order to get startup polarity
correct. Just a quick zap to provide some residual magnetism.

A wound alternator needs some DC to start up, one reason you can't
push start a car with an alternator and a totally dead battery. When
I was a kid, my dad took me to visit one of the sites he was currently
working on, was a rural diesel power plant that had had a crankcase
explosion and was being rebuilt. Got the tour from the guys in
charge, had a huge V-16 engine attached to this dinky gray cylinder
about the size of a garbage can. I asked what that was, they said it
was the alternator. Had a tray of batteries sitting on a cart, were
the old squarish cells they used to use for doorbells, all connected
in series. That was the starting DC for the alternator when they were
going from blackout conditions, no juice anywhere.

An AC motor may work as a generator, but you'll have to provide some
method for providing and controlling the field current.

Stan