OK, my comments were somewhat hypothetical to begin with and I will indeed
research the subject.
>With out boosting the field voltage way above 12V the maximum
>current available will be very close to the device rateing.
Yes you are right, please pardon me. Although I was supposing that the
field current would be present under the conditions I described (I wouldn't
presume that an alternator with no field current could put out much power)
you are right, you would still need more than 12V to get additional output
from this alternator.
BTW, I don't think that it is technically correct to say that magnetic
properties limit the output from the Lucas alternator. My (educated) guess
would be that it is the resistance of the field windings which limit the
magnetic excitation current. By increasing the voltage across the field
you can increase the excitation of the stator windings to the point that
the magnetics saturate. I would think that the field of the Lucas part is
far from saturation under normal battery potentials. I conceed that
controlling the field resistance builds in current limiting for the
alternator since the battery voltage will never be much more than about 15
volts. Field resistance is why the Lucas part will only put out 35 Amps.
The welder I described did not appear to be constructed using a custom
alternator. The rectifiers were external because they could not possibly
survive at the case temperatures that this alternator was run at. I
suppose given the correctness of your statement quoted above that the
output current of the welder was controlled by varying the field current
but at potentials well above 12V. Since the peak output voltages from a
typical alternator can be much higher than 12V when the output is not
loaded by a battery these higher field voltages are readily available. In
fact I believe you need 30ish volts for most arc welding processes, this is
easily obtainable with an ordinary car alternator which is not loaded by a
12V battery assuming the rectifiers can withstand the additional voltage.
Thanks for the correction. It would be nice if next time you wern't quite
so sarcastic about it, my original comments were not ment to offend you and
I am sorry if they did. We all make mistakes, even those of us who attend
MIT eh?
Frank Marrone MK I Tiger B9471116
marrone(at)wco.com '97 Crown Vic LX
Yamaha Seca 900 (aka XJ900RK)
'79 Spitfire
'66 Ford LTD
'88 Nissan 4WD p'up
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