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Registered Member #513
Joined: Sat Feb 10 2007, 07:30PM
Location: Pointe-Claire, Quebec, Canada
Posts: 19
CW Multiplier: Lots of caps and not sure how to arrange them
Here’s the dilemma:
I’m building a CW multiplier for a future particle accelerator (the vacuum system is coming along strong). The power supply is half a 15 kV 30 mA NST. (terminal to ground)
What’s the best arrangement for these materials to give the greatest performance (and highest potential difference!) In other words : WHAT WOULD YOU DO? Thanks in advance. Attached are pics of the caps and diodes.
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
How much voltage do you need for the accelerator? And how much current?
I have my doubts you will be able to make it work with a NST and those caps. With the 20nf ones it might be possible, but you will be limited to a minuscule amount of power with any decent multiplication ratio.
I would think you would be better off with either a vandergraph, or using an AC fly back feeding some stages of CW multipliers. Not because you can get more voltage (you can't use >7.5kv per stage anyway), but because the current available increases linearly with frequency. Switching from 60hz to 15khz gives you about 200x more current available in the end. However, if you go that route you will need high speed diores, something like string of 15 uf4007's or 10 sf1600.
Registered Member #127
Joined: Fri Feb 10 2006, 03:36PM
Location: Cincinnati, OH - USA
Posts: 44
Might I suggest Steve Ward's site. His CW multiplier is quite well designed. One thing I am not sure of is if the 50/60Hz from that NST is going to be enough to efficiently drive a CW. From my understanding CWs work much better at higher frequencies (say when driven from a flyback transformer).
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
The latter stages can have smaller capacitance without a hit in performance as the current through each progressive stage becomes less and less (thus the voltage drop due to the caps impedance is less). This is the same reason RF drives are prefered for C-W's. You can get your hands on some big ferrites like i use from TSC international ferrite (google them). The cores are about $6 each ($12 for a full core) and they can process about 1500W with the poor copper fill you will achieve with a HV RF transformer (they can really do about 3-5kVA with a good copper fill, for low voltage use). The inverter to drive such a thing isnt terribly difficult to make either (the mazilli/zvs driver would work ok i think). As mentioned, you will need ultrafast recovery diodes after maybe 5khz, other wise diode losses will be large.
Registered Member #513
Joined: Sat Feb 10 2007, 07:30PM
Location: Pointe-Claire, Quebec, Canada
Posts: 19
Steve your multiplier is truly impressive. Something like that should definitely be my eventual goal. In the mean time, if I use the caps I have with the diodes, how low will the output current be for, say, 15 stages with an input of 7,5 kV ? Would it be less than a Vandegraff for the same voltage ?
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CW Multiplier: Lots of caps and not sure how to arrange them
