Hi Ted,have you ever checked / measured the voltage drop of the MOT's under load conditions? Could be a problem because of their strayfield properties. In my 12kVA DC system I use a heavy duty 3-phase transformer beast and even there is a significant voltage drop under load. I'm using an accurate DC-HV meter on the DC output, so I know exactly what is going on there :-) DC voltage without load is 13,3kV, which drops to nearly 11kV under load, although I even use a 5µF smoothing cap after the 6-pulse bridge. I expect this to be an even larger problem when using MOT's...
Regards, Stefan----- Original Message ----- From: "Tesla" <Tesla@xxxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx> Sent: Saturday, April 11, 2015 11:59 PM Subject: Re: [TCML] Inductive Ballast for MOT Power Supply
HiAlthough 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 MOTIMHO 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.htmlThis 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 _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla
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