Re: DC Charge inductor.

["Tesla list" <tesla@xxxxxxxxxx>]

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