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Re: DC Charge inductor.



Original poster: Davetracer@xxxxxxx

In a message dated 5/22/2005 10:48:41 P.M. Mountain Daylight Time, tesla@xxxxxxxxxx writes:
Original poster: "Jim Mora" <jmora@xxxxxxxxxxx>


Hello all,

I am going to build an 18 to 40 Henry choke (multi-taped) DC charge inductor
<continued discussions>.


Jim, I more or less fumbled my way to an 18 Henry inductor by winding about 20 pounds of #11 copper wire (with the heavy magnet-wire type of insulation) on a simple coil mold, then putting a removable core inside, made by hack sawing apart a transformer. Believe me, after all these years of "MicroHenry" and such, it got a little weird working in "Henries".


    I used  E
              -----
               IR

to calculate R since I knew E and measured I. At 120VAC, 6.6 amps were struggling through the coil, which works out to 18 ohms "resistance".

    A few notes:

Without the iron core the inductance was not sufficient to keep a 15Amp circuit breaker from popping. I haven't bothered measuring it without the core.

A Dremel tool is not really adequate for this stuff. I now have a Dremel tool that has two speeds, on and off, instead of a rheostat setting the speed. Live and learn. Something about that "soft" iron wrecks cutters, including hacksaws.

Finding the correct transformer was hard. The one I had used iron laid down in an "E" pattern, then a backwards "3" (an E), and I just cut the fingers off and used them in my core.

A friend of my Dad's suggested I try this, "and by golly it worked", so I'll mention it. Put a *light* metal object on top of the coil and iron. Aluminum is very good. Emphasize to all watching that the ring object it is not iron. Turn on the coil. Ping! The object will go flying upwards. What is happening is a current is being induced in the ring object, which makes an electromagnetic field, and Lenz's law says it opposes (say, North to North) the inducing field, so they fly apart. It'll also be quite warm when it comes down ... you just have an N to 1 step-down transformer, imagine the current!

I have not seen, but have heard from people who have, the "magic plate" which lifts up from the table, and which you can cook eggs on, while it hovers in midair. There's apparently a way to lower the magnetic field in the dead center so the hovering plate is self-stabilizer.

Cooling can be a bit of a problem, what with 800 watts flowing through this puppy. I'd just suggest thinking about adding some 1/4" piping for a few turns and cycling water through. I'm sure people on the list have better ideas.

If you need the #11 gauge copper wire I *think* I still have about 50 lbs, over in storage. I'm in Denver CO and it might be very costly to ship it.

    -- thanks,

    Dave