Mike,
For smaller loads, I'd use a Globar resistor also. For the 20 Kw load,
and to homebrew one with limited resources, they might look into this. I
was thinking about those large grid resistors. If one had two of them,
25 ohms each, but wound in opposite directions, it might work somewhat
by seriesing them. This would be the same as that dual wound resistor in
two sections with the different hand coils. The bifilar has a lot of
capacitance due to the potential difference between the incoming and
outgoing resistance wire. But, if this was broken up like the mentioned
in sections, it may work also. One would have to use some sort of alloy
tubing with the highest resistance you could get. For 20 Kw, were
probably talking something like 3/4" diameter tubing with maybe a 1/8"
thick wall or larger. Inco Alloys (Now named Huntington Alloys), has
both the alloy mill (Huntington, WV.), and the tubing plant just down
the road in Burnaugh, Kentucky. They make about every nickel alloy,
(Inconel, Monel, etc.), and others you could mention. I had a friend who
retired there and he may know about this, I'm not sure. Even using that
figure eight pattern might be better. It has a figure eight wound every
other turn so to continuously reverse the current flow from one turn to
the next. With stiff enough tubing, this might be done without using a
coil form.
I'd like to experiment with this some myself just to see what will work
and what will not. For loads of 5 Kw and down, I'd stick with the Globar
resistors.
Will Matney
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