On Sun, 04 Mar 2007 17:30:24 -0000, firstname.lastname@example.org (Gary Heston)
Just a word of experience. Some generators don't play well with
welders. I had a very nice Yamaha 5kw and have a Generac 8kw and
neither play well. The Yamaha would burn out its voltage regulator
rapidly. After repairing it a couple of times I re-designed it to
make it last. The Generac de-excites for a moment (the arc goes off)
and then it comes back up.
In both cases, the problem is the very rapidly and widely varying
current draw. The Yamaha's voltage regulator tried to keep up and
ended up burning out its pass transistor. I redesigned the regulator
with a heavier pass transistor and a switchable long time constant
filter in the input. That kept the regulator alive but the resulting
poor regulation didn't make for very good welding. One could make a
weld that would hold but it wasn't pretty.
The Generac, even though it has more than enough capacity, simply
can't be used. The output shuts down moments after the arc is struck.
I'm sure it's a similar problem but I've not had a chance to look at
I have a homemade 10KW diesel generator that uses one of those cheap
Italian aluminum framed alternators that Harbor Freight and Northern
sell. It's "harmonically regulated". That is, the stator has an aux
winding that is resonated to the 3rd harmonic by a capacitor. The
field rotor is nothing more than a 2 pole electromagnet with a diode
across the ends. The rotor forms the secondary of a transformer at
the 3rd harmonic and the diode half-wave rectifies it to excite the
field. Fairly new architecture - the patents date to the 70s.
Anyway, this unit works fairly well for stick welding but very poorly
for MIG. Regulation is inherent in the design and does not rely on
electronics. The problem with MIG is that the MIG welder depends on
there being great surge current available from the line to blow the
bridge each time the wire shorts to the work. The utility supplies
that but a small generator can't. My rather high end Miller contains
some storage capacitors to reduce the surge draw but it's still there.
I can weld with this generator and MIG but it is rough and unstable
and the weld looks messy. I consider it emergency use only.
If you have much welding at all to do I suggest getting the
combination welder/generator. Those are designed primarily for
welding with the 120 vac output thrown in for good measure.
John De Armond
See my website for my current email address
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