Re: automotive alternators, three phase, RSG

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-uswest-dot-net>" <jimlux-at-earthlink-dot-net>


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> This I like.  It suggests that "high" frequency ac power may
> be cheap and readily available.  Most of the stuff I have on
> spark transmitters, where it relates to the commercial ones,
> states that the mains supply was 400, 500 or 800 cycles,
> which means all manner of benefits accrue.  I've fancied
> getting hold of a 400 or 800 cycle rotary converter to play
> with, but I have so many other things on the boil at the
> moment I scarcely have time (and I have even £?$$ of the
> folding stuff) so a cheap way of doing this appeals. I also
> did not realise that auto alternators are three phase - is
> this universally so - does that hold for truck alternators
> too?
Yep... The advent of inexpensive semiconductor rectifiers was the death
knell for the old generators.  No commutator, just 3 slip rings and a 6
diode bridge.  Ripple's fairly low as well.

I've also contemplated turning an alternator into a synchronous 3 phase
motor for "traction" applications. In stock trim, they get a kW out of them
as generators, so you should be able to turn one into a several HP ac motor.


>
> Anyone know if it's OK to use standard 50/60 cycle
> laminations at these frequencies?  I know eddy losses will
> be up, but don't know how acceptable this is.  Any list
> members with 400-800c/s power experience?  I do know that
> higher frequency ac uses less turns per volt for the same
> core size, I may even have reference books on the shelf with
> the necessary calculations in them.

I've run 400 Hz through 60 Hz transformers without any obvious problems, but
it was very low power.  The most annoying thing is the higher pitched
singing of the laminations, etc.  50/60 Hz makes a low pitched hum, 400 Hz
makes a most annoying whine.  Think of that high pitched constant whine you
hear on an airplane, particularly on the headsets.... It really gets to you
after a while..

The big problem is going to be using an NST.  The current will limit at a
value lower by the ratio of the frequencies (i.e. a 15 kV/30mA 60Hz unit
will limit at 3 mA at 600 Hz...)