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Re: [TCML] charging reactors



Good points Ed.

You know, I've been a crappy guitar player since I was 5. With that experience, I couldn't help but look at Hammond Manufacturing when Jim mentioned the "charging inductor" (many good tube amps use Hammond RF Transformers). Hammond does build a 5H 500mA choke which would suffice for this application if it were not for the high voltage. Voltage is a big problem here with the charging inductor. In order to create the voltage winding standoff, the insulation thickness becomes a burden on winding a 5H inductor. Even the 5H 500mA choke Hammond produces (193P) is about the size of a hefty MOT, and it's rated at only 800V. It's not an easy assignment as stated earlier. Digikey offers the 193P at $170. I can't imagine what a 10 to 20kV version would run if there were such a beast.

Regards,
Bart



Ed Phillips wrote:
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
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