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Re: Inductor question
>Date: Sun, 8 Sep 1996 12:21:59 -0700 (PDT)
>From: "Edward V. Phillips" <ed-at-alumni.caltech.edu>
>To: tesla-at-pupman-dot-com
>Subject: Re: Inductor question
>
>For what it's worth:
> I have an adjustable ballast for mercury vapor lamps
>here which uses an E-I core which is held in a cast frame such
>that the air gap can be adjusted by moving nuts on a pair of
>bolts at the side of the frame. Seems to me an arrangement like
>that would work real well. Get a big enough transformer core,
>put enough turns on it to withstand the maximum voltage you
>expect across it, and then open up the air gap and "tune for
>maximum good". Once the right gap was found you could cut some
>insulating material of the same thickeness, and then tighten up
>the bolts until the humming wasn't too bad.........
>Ed
>
I spent Sunday playing with this idea. I was using 148 turns of #17 on
a 300VA core. (I had 5 110V 300VA power xformers primaries wound for
me a while ago.) I used these at 110V for ease of measurement. I don't
have hard numbers yet but I'm working on them.
I was gaping the I section of the E I core with 0.003" pieces of paper
and found out what a big difference in the inductance of the coil that
made.
Open core I = 2.85A (300watt lamp ballast;)
Closed core I = 0.5A
3mil air gap I = 1.2A
More Later,
jim