"Jim Adney" wrote in message
...
On Sunday, 29 Aug 2004 00:20:10 -500 "Asimov"
wrote:

Fred, how does the iron lose all its magnetism in the first place?
I thought that by design there was always supposed to be enough
residual magnetism to bootstrap the generator...

You're right that there's little reason for residual magnetism to go
away. An automotive generator can sit for years or decades and still
be fine.

That's just for DC generators, however. I don't think there are any AC
generators of any significant power that use residual magnetism to
bootstrap themselves. They all require a bit of current from some
source to get themselves started.

The one exception might be brushless AC generators, which I thought
were rare. They could be designed to use residual magnetism to get
going.

Does this AC generator have any brushes?


Quite a few portable generators excite themselves from residual magnetism,
and yes they have brushes on slip rings.