"Jim Adney" wrote in message
...
On Tue, 31 Aug 2004 02:14:48 GMT "James Sweet"
wrote:

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

I'm always glad to learn something new, but then I have to wonder why
automotive AC generators (alternators) don't do this.



Because they have a battery to do it for them. The field coil is powered
through the voltage regulator which recieves power from the battery when the
ignition is on.