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Re: automotive alternators, three phase, RSG



Original poster: "Eric Davidson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <edavidson-at-icva.gov>

Jim et al,

The automotive alternator would be a good way of generating 3 phase current.
But there are several considerations that need to be addressed.  The voltage
would have to be stepped up to power a NST, and while a 12/120 volt
transformer is easy to come by, you will have to find some way to get the
output frequency of the alternator at least close to 60 Hz.  Another issue
is the power output.  Most alternators put out less than 100 amperes at
12-14 volts (only 1200-1400 watts) not too shabby for an alternator, but far
short of  *pole pig power*.  Putting several alternators in parallel,
especially if they are dissimilar (likely,  from a pick your part junkyard)
would be very challenging.  The issue of a suitable motor to drive the
alternator must be addressed.  A 2-3 hp motor would be required.  A couple
hundred dollar expense if you have to actually buy one. The correct speed
must be determined (for 60 Hz output) and supplied via some sort of pulleys
or the like.   The most complex task will most likely be voltage regulation,
not easy for a wildly varying load like a Tesla coil with its spark gaps
etc. Hope this helps. Coil safe

Eric
edavidson-at-icva.gov


> Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<jimlux-at-earthlink-dot-net>
>
> It occurs to me that an interesting experiment (I'm a great one for ideas
> for experiments, but I rarely actually get a change to try them) would be
> to rig up a big motor (gas, electric, hamster wheel, it matters not)
> driving a 3 phase alternator (as from a car, with the diodes removed) and
a
> rotary spark gap on the same shaft.  By definition, the phasing of the
> spark gap will be locked to the electrical phase.  You can change the
break
> rate by changing the speed of the prime mover (crack the whip on the
> squirrels) and you can change the output power by changing the field
> current on the alternator.
>
> You could probably drive 3 NSTs with the alternator (or maybe GMHEI
Coils),
> then feed each one through a set of gaps, all feeding a common primary
> capacitor/inductor, at high break rates.  Maybe even 3 static gaps might
> work, if properly set. Or, for a real weird setup, how about 3 primaries
on
> the same secondary?
>
> The NST won't put out much current (the frequency will be higher than 60
Hz
> from the car alternator so the leakage inductance impedance will be higher
> in proportion... I think they run several hundred Hz.. Anybody know how
> many poles the typical alternator has?
>
> This has the nifty advantage of having no electrical connection to the
> power lines, so back conducted EMI isn't an issue (for that matter, you
> could run an insulating shaft through the wall of a faraday cage and have
> your three phase TC totally isolated).
>
> Before you all leap on me, I know that Tesla built systems just like this,
> and they were also used in commercial radio in the days of spark.
>
> The interesting thing here is that it uses cheap parts: Alternators cost
$5
> at the "pick your part" junk yard, and dead alternators are even cheaper.
A
> dead alternator is usually dead because one of the diodes (or the internal
> regulator) has failed, and you would remove those anyway.
>
>
>