[TCML] charging reactors

[Ed Phillips]

jimlux wrote:

> Ed Phillips wrote:
>
>> So, if one needed to build or buy a dozen charging inductors for a 
>> resonant charged spark gap coil, where would one look..
>>
>> It's for an application where there's multiple coils being charged 
>> from a common HV DC bus.
>>
>> Probably need 5-10 H, and it needs to handle a few hundred mA to amp 
>> (e.g. 10kW @ 10kV is an amp), and, of course, have a 10-20kV voltage 
>> rating.
>>
>> --------------------------------------------------
>>
>>    That's a mighty big assignment!  Those things will be expensive if 
>> you can find them at all.................
>>
>
> Well.. I've seen some websites with TCs where folks wound several 
> hundred turns of wire on a Ferrite U core of some sort or another. I 
> suppose one could find the bare cores for MOT's for instance. (or a 
> cheap source for the transformers new, and just saw off the windings 
> you don't need..)
>
> Just casting about for ideas..  And expensive is a relative term.... 
> $50 each wouldn't be unreasonable.

    I hate to be negative but you're talking about really serious chokes 
here and nothing you can do with "several hundred turns on a U core".  
You want a lot of inductance with a lot of DC flowing through the coil 
and that's something you're not going to get by casual experimentation.  
I would guess you'd need a high-quality transformer iron core with cross 
section of at least 4 square inches, a fairly large air gap, and lots of 
wire with special attention to insulation.  You can probably find power 
inductor design information on the web if you hunt around.  If you can 
find something meeting your qualifications for $50 that would be a super 
bargain!  I'm looking at a 1958 Stancor catalog and see that a 6 henry, 
500 ma choke has a base size of 5-5/8" x 5-1/2" and is 8-1/8" high.  
Shipping weight is 24 pounds and list price 50 years ago was $54.00.  A 
10 henry, 1 amp choke from UTC is 4-3/4" x 6-7/8" x 10-1/2" and weighs 
40 pounds.  Net price was $40 half a century ago!  Neither of these 
transformers is designed for high pulse voltage across the windings and 
that would of necessity require more insulation with more iron and more 
copper.

Good luck,

Ed