Re: <tap><tap><tap> Is this thing on???

In article <slrnerqehn.74k.andrew+usenet@xxxxxxxxxx>,
Andrew Dalgleish <andrew+usenet@xxxxxxxxxx> wrote:

In article <C1E0EE82966871D04@xxxxxxxxxxxx>,
Chris Suslowicz wrote:
In article <jaFuh.2298$yG5.1785@xxxxxxxxxxxx>,
mroberds@xxxxxxxxxxxxxxxx wrote:
In these latter days, it'd probably work better to generate AC at a
freqeuency determined by the input speed, rectify to DC, and then
invert to AC at the desired frequency. Diodes last a lot longer than
carbon brushes.

You still use carbon brushes, I'm afraid to say.

(Well, apart from the /really/ tiny stuff.)

Or the really big stuff, or anything in between.

Really? While I freely admit that I haven't been close to any large
electric motors or generators for some time, I think the generators
at least still use brushes, as does any non-synchronous AC motor.
You've got to get current into or out of the rotating bits somehow,
and that implies slip rings or a commutator of some sort. I doubt
that anyone will be making large electrical machines with permanent
magnet rotors (or stators) for a variety of reasons. (Not least the
inherent difficulty of assembling the thing, plus the tendency of
the magnet to attract swarf, shipyard confetti, spanners, et cetera
while out of its housing.)

Traditional generators had a DC exciter to allow you to vary the
output voltage while maintaining constant RPM so that you could
match phase, connect it to the load and then crank up the output.

Chris.

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