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Re: Ballast inductor.
In a message dated 10/2/00 6:12:15 PM Pacific Daylight Time, tesla-at-pupman-dot-com
> Original poster: "M Fabs" <the_machin_shin-at-hotmail-dot-com>
> I just wound 100 feet of #10 romex THHN wire onto a 2" dia pvc conduit. I
> also poly'ed a bunch of welding rods together to fit inside. I am hoping
> use this as a variac substitute, a variable inductor. I measured the
> inductance with the rods in the coil and with them out of the coil, and
> numbers I found are 1.72millihenries with the rods fully inserted, and
> 330microhenries with them not inside. (That last one might be off a bit, I
> was paying more attention to the full insertion number.) 60Hz 120Vac
> standard wall outlet is my power source. I forgot the formula for
> reactance. Anybody willing to crunch the numbers for me and tell me what
> current range this will allow me? Another option is to arrange a brush
> to use like a true variac. Just looking for some idea as to how useful
> will be, or what changes I ought to make. Thanks folks.
I have a homemade ballast, but I didn't build it. I think it has 300 turns
of #12 wire, with a bunch of taps. Originally it was filled with welding
rods and threaded rods, but I replaced that with transformer "I's" from
NST's. Max inductance is about 26mH, minimum is about 1mH.
This gives the range that I need. The range that you need will
depend on the coil specs and voltage input. The form for the
ballast is 3" by 19" pvc. A large selector switch selects the
8 taps as needed.