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alternators for 3 phase power...



Original poster: "Jim Lux" <jimlux-at-earthlink-dot-net> 

Subject: Re: Problem with common leads in dual channel scopings?


 > Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>
 > >I have a Delco Remy Car Alternator that
 > >I have converted to three phase AC, with pulley
 > >arrangements made to procure 480 hz I just put this
 > >thing through some grueling tests, not a wise thing to
 > >do since the amount of internal heat generated at the
 > >end of these tests was probably enough to start
 > >melting the insulation, and I could smell that
 > >starting to happen. At the end of these tests I was
 > >making 46.7 volts with some 9 amps. (which might be
 > >considered about 420 watts output!)
 >
 > Most alternators can do 60 amps..  12V x 60 = 720 watts.  I would think
 > your alternator would run cool!!

What's the rotating speed of the alternator (i.e. is it a 2 or 4 pole
device...)... The 60 Amp output from the alternator is typically with the
engine running at >3000 RPM, and the alternator is "geared" (actually
"belted") to run somewhat faster than the engine.  I assume that you're
measuring the voltage with a significant load (i.e. to draw that 9 Amps at
40 V).. It's very possible that you'd get more power out with a different
load impedance.   And, is that 9A from each of the three phases with the
voltage measured in Delta or Wye/Star?  If that's per phase, then 360W*3 is
a fairly respectable output.  I'd expect, though, a current (per phase) on
the order of 20 Amps without overheating.  Maybe it's the field that's
overheating?  Also, recall that the usual alternator is running in a
respectable amount of airflow from the radiator fan or motion of the car,
albeit with air at 180F or so...

Unloaded, most automotive alternators can easily put out 120V DC with
sufficient field current (limited primarily by the breakdown voltage of the
bridge diodes!).. Many times have I contemplated building the proverbial
million volt power supply by stacking 50-100 kV stages each with their own 1
kW alternator, driven with an insulated shaft (Quite Rube Goldberg,
though... there are much easier ways, but, thinking in terms of free labor
and junk parts from the scrap yard...)  I'll bet you could run a NST off a
single phase off an auto alternator... If it's a 2 pole device, then, 3600
RPM -> 60 Hz... Have to go look at one out in the garage and count windings
on the stator.  If you had a big pile of free NSTs and free diodes....

If  you're paying for it, though, it's probably cheaper to just go out and
buy the right transformers and rectifiers...

 >
 >
 >
 > >Variac Volts/DC field Amps/ Stator Volts
 > >
 > >10 .04 A 2.55 Volts
 > >15 .21 A 5.28 Volts
 > >20 .41 A 9.11 Volts
 > >25 .60 A 13.4 Volts
 > >30 1.04 A 21.6 Volts
 > >35 1.32 A 26.5 Volts
 > >40 1.63 A 30.3 Volts
 > >45 1.94 A 34.7 Volts
 > >50 2.28 A 38 Volts
 > >55 2.58 A 40.6 Volts
 > >60 2.92 A 42.8 Volts
 > >65 3.2 A 44.2 Volts
 > >70 3.52 A 45.3 Volts
 > >75 3.8 A 46 Volts
 > >80 4.05 A 46.7 Volts
 >
 > Interesting data!
 >
 >
 > >I think for now this thread has become very off topic,
 > >and Terry may be getting the ax out, so when it
 > >becomes more relevant by the building of an alternator
 > >based tesla coil, more posting of alternator work will
 > >be made.
 >
 >
 > Cool!
 >
 > Cheers,
 >
 >          Terry
 >
 >
 >
 >
 > >Sincerely HDN
 >
 >