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RE: [TCML] charging reactors
For what its worth, I wondered "What would Tesla do?" If he needed an
inductor, he didn't worry too much about space in his lab or the cost of
wire.
My thought was, hey, just make it bigger in diameter since L goes up
(approximately, for large diameters) by the square of the diameter.
My initial calculations tell me that larger diameter will break the bank in
terms of total wire length.
In my search, I found this:
http://www.pronine.ca/multind.htm
Any way, just thoughts for a snowing morning here in Utah.
Jim Harvey, W7YV
-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of bartb
Sent: Wednesday, March 04, 2009 8:59 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] charging reactors
You certainly don't want to use THHN sized insulations and a single layer
would not do. Magnet wire is the preferred choice here. The voltage is
distributed through the winding and you want to attain the inductance in the
least amount of "space" with the minimum voltage stress across the worst
case opposing layers. A single layer is not possible without getting
ridiculous with geometry.
Everyone seems to be thinking in terms of heavy gauge and heavy insulation
wire. If I remember Jim's specs, it was 10kv to 20kv in the 500mA to 1A
range at about 5H. This really isn't that difficult to achieve. For example,
consider a 1"D x 4.3"L core. Now imagine 100 layers of 30Awg magnet wire.
The result is a 5H inductor good for 1A and the worst case stress across the
layers is 400V with 20kV applied.
Obviously, this wire size is small, DCR is 166 ohms and net impedance is
1.88k ohms. You could zap this wire size with too much current if no current
margins were taken into consideration. So maybe head up to 2"D x 4.75"L core
and use 24 Awg (robust). This inductor ends up an outside of 6.5"W x 4.75"L.
Pretty hefty inductor, but it could be wound on a bobbin and would certainly
do the job. Because the layers are still 100, the voltage stress is still
near 400V worst case across joined windings.
Anyway, there are many layer/winding possibilities, but magnet wire is what
you want here. Going with a thick insulation (if thinking about voltage
standoff) is not practical nor is it needed in this case. I know Richie
Burnett wound his large ballast with thick insulated wire, but the
inductance was in the low mH range (it's a ballast application).
Quite a different cookie than what would be needed for Jim's need.
Take care,
Bart
Ed Phillips wrote:
> What about a straight, stick-shaped core? Think in terms of an
> old-style induction coil, but with only one winding. This would
> greatly simplify homebrewing, as bundled iron or steel wire could be
> used for the core, and the winding would be a simple solenoid. Isn't
> a straight core like this more resistant to saturation than a
> shell-type core?
>
> Cheers,
>
> Greg"
>
> Answer to last question is certainly. Problem will be the size of
> the thing to get the desired inductance when wound with wire that can
> handle the current and insulated for the high voltage. Almost
> certainly impractical even with very modern core materials. Iron or
> steel wire wouldn't do - would need a large laminated stack.
>
> Ed
>
>
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