Re: Ignition Coil for DC Resonant charging

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

At 12:39 PM 1/7/2003 -0700, you wrote:
>Original poster: "Stephen Conner by way of Terry Fritz 
><teslalist-at-qwest-dot-net>" <steve-at-scopeboy-dot-com>
>
>At 08:19 07/01/03 -0700, you wrote:
>>Original poster: "S & J Young by way of Terry Fritz 
>><teslalist-at-qwest-dot-net>" <youngs-at-konnections-dot-net>
>>
>>
>>Steve,
>>
>>No experience with ignition coils, but I have used 3 and 4 MOT secondaries
>>in series successfully with a DC resonant charging circuit.  You will find
>>that the more inductance you have, the slower you can run your ASRG before
>>it power arcs due to the gap dwell time being too long.  I believe ignition
>>coil secondaries would overheat from the current going through them.
>>--Steve Young
>
>I found some ignition coil data on Jim Lux's website and plugged it into 
>my PSpice simulation. The ignition coil secondary would be dissipating 
>about 50 to 60 watts of heat. The power loss isn't a problem in my system, 
>but if the coil overheats and bursts it wouldn't be too good. As for the 
>inductance: I know more is better but I understand that too much will 
>eventually mess up the performance at the high end. I'm going for 400bps, 
>20 to 30 Henries is about right for my system and if I can get that from a 
>couple of MOTs that would be great.

Hmmm.. that seems like a LOT of power to be dissipating in some mighty fine 
wire.

You might take a look at http://www.alphacore-dot-com/inductor.htm .  They make 
tapewound air core inductors intended for audio crossovers. Add an iron 
core, and you're all set.  From the description on the datasheet (I haven't 
actually broken down and bought one yet), they should handle many kV 
without breakdown, because it's basically a thin (12/14/16 AWG equivalent 
cross section) metal ribbon wound with some plastic film (1.5 mil 
polypropylene) and heat sealed into a "block".  The voltage stress across 
the dielectric would only be the turn to turn voltage, which would be well 
within the dielectric withstand of the plastic.

Granted, these things are only millihenries, but put a core with a 
permeability of, say, 5000 in the middle (checking the cross sectional area 
to make sure it doesn't saturate!) and that 1 mH inductor for $12 becomes a 
5H inductor.  The same company probably sells the cores....