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Re: 40 Amp variac ballast
In a message dated 9/21/98 9:16:25 PM Central Daylight Time, tesla-at-pupman-dot-com
writes:
>
> Tell us about your steel band inductors. I'm planning to experiment with
the
> same material after I get my coil running.
>
> Thanks,
> Brian
Brian, all..
Several years ago I experimented with different core materials for
inductors. The first core was actually wound with steel antenna guy wire. A
round form made from wood was used on my coil winder to assemble it. #10 THHN
wire was wound over the coil making random taps along the way. The total
inductance available was 8 mH. A high power switch was made on a 1/4" piece
of phenolic using 3/8" bolt heads as contacts, which there are 30 of. The
switch wiper was a steel strap welded to a spring loaded shaft mounted in
bushings, and the wiper itself is made of 3 bronze vehicle starter brushes
soldered together on a pivot. This "switched inductor" is still in use today,
mounted in my control cabinet.
As time went on, I needed a larger inductor. At a salvage yard, I picked up
a roll of 1" x .030" steel strapping, very heavy. 4 individual rolls were
made, having a cross section of 1" x 3", then tack welding the ends to keep
them together. Then they were taped together with cellulose strapping tape to
make a 4" wide core.
It was wound with 200' of #14 romex (house wiring) sheath and all. All taps
made had each of the 3 internal wires (white, black & bare neutral) soldered
together making the combined current handling greater. I don't have the
inductance value handy for this core, but it is used to ballast two 7200 volt
pig's low voltage inputs in parallel.
On all toroid cores, the wire was wound on a flat plywood shuttle, then
passed through the center of the core to wind it.
I know it's not a perfect metal to use for a/c powered inductor cores, but
in Tesla Coil use the duty cycle is low enough that core heating from eddy
currents and hysteresis loss are not a problem.
Hope this helps
Kevin E.