Re: alternators for 3 phase power...

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

Original poster: Harvey Norris <harvich-at-yahoo-dot-com> 


--- Tesla list <tesla-at-pupman-dot-com> wrote:
 >  > 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...)...
7 pole face rotor on each side equates to 7
cycles/alternator field rotation.
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)..
I cited loads of 12.5 ohms here, and of course this
equates to the tripling of the cited current when we
count all three phases, and of course a three phase
rectification into DC would give a much higher cited
amperage output from the alternator.

It's very possible that you'd get more power
 > out with a different
 > load impedance.
Indeed with loads involving resonances of high
capacities this works better then would be suspected
for some tank circuits. One of these using some 80 uf
started smoking wires when I connected things wrong.
In fact it is predicted that the parametric output
could be increased by simply by giving each phase a
sole capacitive load of 500 uf, which would be a value
predicted to resonate with the internal inductance of
the statorat this frequency, if such things are
possible?  To understand what I say, lets suppose the
1.5A short drawn from a phase without the field
energized, lets just suppose that a majority of the
R(INT) stator value that makes this reading is due to
the stator impedance, instead of just the resistance.
A capacity placed as a load on the unenergized field
stator will always deliver a higher voltage then its
equal impedance inductive reactance counterpart. So I
am fairly sure it should be possible to pull more
amperage out of the alternator, then what the
alternator will pull at dead short, for any condition
of field energization, where here we are limited to
low levels of field energization.. I could
reinvestigate a simple instance of this, if need be to
any doubters, which of course it does make me have
doubts also, as to whether what I am seeing is real!
Mistakes do happen... But say we calculate the
impedance and capacitive reactance that would
establish a current of 1.5 amps, given the 2 volt
parametric measurement of 2 volts. The moment we place
that high capacity as a load on the alternator, the
amount of reactance cancellation on R(int) acts to
raise its stator voltage, so it would (seem) that the
1.5 amp limit extracted from an unenergized field in
rotation (obtained at this rpm) might be exceeded for
certain loads.


  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.
Yes on all three phases.
  I'd expect, though, a
 > current (per phase) on
 > the order of 20 Amps without overheating.  Maybe
 > it's the field that's
 > overheating?
Yes people may not realize that an alternator can
overheat when no load is placed on the outputs! The
stator windings are connected in wye, and internal
amperage ciculation will occur depending on the amount
of energized field being employed. Because of variac
control, instances of the alternator being run in
"Overload" mode, such as trying to resonate a 1/4 ohm
spiral, the resistance of the load may be lower then
the resistance of the internal stator, so we are
technically operating in overload mode, but this is
being regulated so that overheating does not in fact
take place. Such a circuit seemed to gain excessive
field heating however when it accidentally went open
circuity by blowing the amperage fuse of the meter
monitoring the amperage. More internal amperage
occured that what the load had negotiated under the
unusual circumstance of overload operation. This is
another thing that needs retesting, because it sounds
so dubious...

HDN