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Re: Ballast inductor.

1.72 mH = 0.65 ohms reactance = 380 amps at 240VAC short circuit!
0.33 mH = 0.12 ohms 

I'd try winding a few more turns.. Inductance goes as the square of the
number of turns.
Don't forget that your 100 ft of #10 has a series RESISTANCE (not
inductance or impedance) of about 0.1 ohms, also... (rule of thumb, #10 = 1
ohm/1000 ft)

Also, saturation might be a problem.  That is, the current might be high
enough to saturate the core, which will make the inductance closer to the
"no core" value.

> From: Tesla list <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Ballast inductor.
> Date: Monday, October 02, 2000 5:08 PM
> 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. 
> 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,
> 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.
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