In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.
Subject: Re: Yet another fusor attempt
Date: Sep 22, 12:38 pm
Poster: Jim Lux
On Sep 22, 12:38 pm, Jim Lux wrote:
>I'm not quite sure where to find three isolation trannies at $50 each- tell me the secret!
C&H Sales Co, 2176 E. Colorado Blvd, Pasadena, CA 91107 tel 800-325-9465 (I don't recall the web URL, but it's out there somewhere. http://www.aaaim.com/CandH/ ??). 15kV 110V:110V 500VA isolation transformers..
You're right, that would certainly simplify my situation. I could use a non-isolated, half NST followed by doublers, but the problem there is that while I have fewer stages, I have to have higher-voltage more exotic parts.
What exotic parts? The rectifier? Get the 6kV 200 mA diodes from All Electronics in Van Nuys, CA ($.40 each, last I checked) and string 20 in series (120 kVPIV) and pot them in silicone (2 part RTV) or sink it in oil. You want massive overdesign on series strings to account for variability of the devices, etc. They're cheap, so the extra 5-10 units is only a few bucks.
Microwave oven rectifiers are essentially the same devices potted into an epoxy block. They're very expensive for the ratings when bought new, and of uncertain quality when scrounged.
You can use the microwave oven caps for filtering, by just stringing them in series. They have resistors across them already for equalization. You might also want to consider a choke input filter, rather than capacitive... less stored energy in a flashover.
The microwave transformer allows the use of the microwave caps and diodes. Yes, it's a tad bit dangerous. Do you have any pointers to x-ray equipment liquidators online? Certainly the power demands are not too heavy here.
You might check out the power transformer rebuilders like Austin or T&R for a potential transformer designed to run off a 60-80 kV line.
For state of the art cool, and a power supply that I am contemplating for fusor use, build a high frequency switcher driving a voltage multiplier. With this you could build a constant current or constant voltage or anything in between. The high frequency means the caps are smaller (cheaper).
>>>>I wouldn't fool with microwave oven transformers or the like... How much current do you really need? Aside from a surplus Xray unit (the best solution, probably), you might do better with some 15 kV neon sign transformers ($80 new) and some 15 kV isolation transformers ($50 used), which will give you 45 kVRMS, and near to 60 kV rectified and filtered. Add another NST and a pair of isolation transformers, and you're up to 80 kV.