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Re: [TCML] Inductive Ballast for MOT Power Supply


Although I've used exactly the 4 MOT PSU design you are using over time I've been converted to DC designs for stability and ease of management. Silicon is cheap and over design makes life reliable and simple. I am a MOT fan as they are very cheap and used creatively can support high power coiling on a budget or low power with a single MOT

IMHO the best way to go is to use MOT's in a DC resonant charging design. I have taken your 4 MOT configuration and extended that to 6 MOT's using the same arrangement in both DC and AC modes. I have ALL my outer MOT's in transformer oil. I am ambivalent about floating secondary cores but have found it works. My bible on resonant designs is Richie Burnett at http://www.richieburnett.co.uk/dcresist.html

This arrangement means no current limiting is required as the current draw can be controlled by setting the BPS . I use some power factor correction with array's of MOT's as the charging reactors (gapped a little and secondary's in series parallel arrangements) and also in a pi section DC filter preceded by a FW DC rectifier bridge. The beastie uses a total of 14 (free) MOT's and can run over 10 kVA.

The use of MOT's in DC resonant designs is completely scalable from the single MOT with doubler and level shifters  design pioneered by Steve Conner  at http://scopeboy.com/tesla/tc2schem.html  (his old site) see also Mike Wood's DC coil  at   http://www.capturedlightning.org/hot-streamer/drilling/dcconstruct.html. Unlike Mike I used MOT’s , 2 secondary’s in series gapped to 0.3 mm as the DC resonant charging chokes) 

Good luck and safe coiling
Ted in NZ
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