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Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Firefox wrote ...
Yeah, I have the high bid on the $20 one right now, but I have a feeling its going to jump out of my price range pretty quickly on the last day, unless the guy bidding against me is kind enough to let me have it .
Also, I intend to use this transformer with CW multipliers, starting with 100kV peak. I have the materials to build my own HV capacitors, and I will be investing in some 1N4007s soon as well. I found it incredible that I could make a 200kV PIV string for $2.50. I know I will also need to get some 100kohm resistors for a limiter too.
Not to burst your bubble, but to build a CW multiplier starting at even 70kV as your base voltage, is an extremely difficult undertaking, and going to require a 70kV transformer much more powerful that what a simple x-ray transformer is capable of.
The problem is that at those voltages corona and field control is absolutely necessary and the losses from even a well designed system, are going to be considerable enough that probably a 100mA 70kV transformer would be required to offset the losses and maintain the output voltage (remember, CW multipliers output voltage vary greatly with load). In laymens terms, thats a transformer that can put out almost 7000Watts continous which is HUGE. Its going to be oil filled and probably weigh about 500 lbs not to mention extremely - extremely difficult to find. (34.4kV are about the highest voltage transformers at those power levels which are not impossible to find - salvage yards in VA by Richard Hull's place is supposedly a hot spot although you may only find one every year or so. Rumors has it a guy named Alex has a lot of big transformers still which he may be willing to part with)
Also, those diode strings aren't going to cut it either. To minimize losses, you'll need to likely pot those in a potting compound or put inside an oil filled canister to minimize corona loss. Same with the capacitors and other interconnections.
And for proper corona and field control, based on my experience with CW design, including commercial designs i've done for several clients at those voltages, your talking a CW multiplier thats going to stand more than 10 feet tall and probably at least 5 feet in diameter.
My recommendation, would be to stick to a CW multiplier that has a max. output of say 100kV . You could use a 14.4kV, 1.5kVA potential transformer which are relatively easy to find if you search hard enough, or just use a simple high power flyback. Dr. Resonance of Resonance Research has nice flyback transformers he used to sell. Drop him a line, and he may be able to sell one for about $50.00 or something like that.
Or check out Steve Ward's high voltage website. He has a nice CW multiplier which puts out about 90-100kV which is based on a homemade flyback i believe.
If you want to generate several hundred kV, then just build yourself a tesla coil or DRSSTC. The DRSSTC is nice since you don't need a specialty transformer, and don't need to worry about corona and field control like you would in a CW multiplier.
Registered Member #1389
Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346
Thank you for your insight Dr, Gigavolt. If you don't mind (since it is a bit off topic here) could you PM with the considerations taken with E-field control and design of the multiplier itself, or a place where I can read about such things? If I am not going to build the CW, then I might as well turn this into a learning experience. I have had certain fascination with CW Multipliers since I first built one from disposable camera parts. I have two right now (both need repairs), one with a 9kV output and one with a 7kV output. To be honest, I am somewhat disappointed that it is so difficult to pass 100kV with a conventional CW multiplier.
Also, if it isn't against corporate something or other, would you mind showing some pictures of the multipliers you worked on?
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Firefox wrote ...
Thank you for your insight Dr, Gigavolt. If you don't mind (since it is a bit off topic here) could you PM with the considerations taken with E-field control and design of the multiplier itself, or a place where I can read about such things? If I am not going to build the CW, then I might as well turn this into a learning experience. I have had certain fascination with CW Multipliers since I first built one from disposable camera parts. I have two right now (both need repairs), one with a 9kV output and one with a 7kV output. To be honest, I am somewhat disappointed that it is so difficult to pass 100kV with a conventional CW multiplier.
Also, if it isn't against corporate something or other, would you mind showing some pictures of the multipliers you worked on?
The limiting factor is the transformer (or source) at those voltages. Think of the design as a giant balloon being filled with water. Lets say voltage (pressure) is how much the balloon is inflated. Now with low voltages, you'd simply put a low pressure water source and blow that up to say your 20-30kV. Now, once you hit about 45kV, you start running into coronal losses. Let those coronal losses being pin holes in the balloon which vary in number according to how much the balloon is inflated. As you approach 100kV, those holes being larger holes, and much more water is being drained through those holes than is being pumped in by your source. Now you really need to up the input source to overcome those losses. Increase the voltage more, and those holes get bigger and bigger. Finally, to keep going you need a monster transformer source to keep you going.
Electrostatic field control and corona suppression is a topic capable of an entire book altogether - definitely not something relayed in a PM. At the very basic, it means eliminating sharp points, and providing necessary distances between voltage gradients to reduce coronal discharge. At the most complicated, it involves complex geometric electrode / shield design.
Just one counterintuitive example is that most would think a spherical electrode or cylindrical connection (i.e. wire connection) above an infinitely flat and large ground plane would be the best arrangement for electrostatic field control. When in fact it is not. The best arrangement would be to mirror the electrode or wire on the actual ground surface. Of course, there is a tradeoff on practicality, and you don't usually see things like this on very large devices, but inside confined areas, these type of electrostatic field controls are employed quite commonly at voltages above 100kV.
Anyways, not to disapoint, but just start out small. You've already built some low voltage CW multipliers, now the next step is to up the voltage some more. Your best bet is to probably get one of those large flybacks from Dr. Resonance. He uses these for his CW multipliers to power his VDG generatores, etc... and they're pretty inexpensive (about $50.00 i think)
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
My CW easily went past 100kV... and yes, i measured it :P. I think i topped out at about 190kV before wussing out.
I used the doorknob caps to also act as field shape control. Because the plates of the doorknob caps spread out pretty far relative to the small "sharp" steel hardware that connects to them, it shields that stuff pretty well. At the same time the cap plates are epoxy potted, so you wont get DC corona formation. The only place i could ever detect corona was at the very top with my ghetto little home made toroids, something nicer would certainly help. I had plenty of current drive though, so corona losses werent a big deal.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Steve Ward wrote ...
My CW easily went past 100kV... and yes, i measured it :P. I think i topped out at about 190kV before wussing out.
I used the doorknob caps to also act as field shape control. Because the plates of the doorknob caps spread out pretty far relative to the small "sharp" steel hardware that connects to them, it shields that stuff pretty well. At the same time the cap plates are epoxy potted, so you wont get DC corona formation. The only place i could ever detect corona was at the very top with my ghetto little home made toroids, something nicer would certainly help. I had plenty of current drive though, so corona losses werent a big deal.
I don't doubt that. Dr. Resonance's flybacks should easily get you to about 100kV and more . . .
I'm mostly talking about using 100kV+ as the input source and using multiple stages above that trying to get 400KV + . . . as the original user suggested.
Registered Member #1389
Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346
Thank you Dr. I tried googling Dr. Resonance, but I could not find where you meant to buy the flybacks from him. What are they rated for as far as input frequency/voltage and output is concerned? You were right about me being overzealous. A nice next step would be a higher power (all my previous CWs were 1-50W) multiplier, somewhere between 50 and 200kV output.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Firefox wrote ...
Thank you Dr. I tried googling Dr. Resonance, but I could not find where you meant to buy the flybacks from him. What are they rated for as far as input frequency/voltage and output is concerned? You were right about me being overzealous. A nice next step would be a higher power (all my previous CWs were 1-50W) multiplier, somewhere between 50 and 200kV output.
From Dr. Resonance post a few years ago . . . (SEARCH Resonance Research in GOOGLE to find contact information)
Original poster: "Dr. Resonance"
We tune ours to adjust to our plasma globe load, usually around 20-22 KHZ.
We run the primary at 120 VAC off AC line with a MOSFET switcher circuit. Rectified output is around 15 kV DC, but in oil they can be operated at high as 17-18 kV DC output. With a voltage doubler circuit in oil at 30 kV DC output.
Max continuous power is 75 watts. We have run them with a doubler on a light load at 150 watts --- charging a cap bank where the flyback only works hard for 5-10 sec.
Dr. Resonance
Resonance Research Corporation E11870 Shadylane Rd. Baraboo WI 53913
Registered Member #187
Joined: Thu Feb 16 2006, 02:54PM
Location: Central Ohio
Posts: 140
Sorry if I missed something in your descriptions, but the thread title says that you want a 60Hz transformer. Anything with ferrite is likely going to be for much higher frequencies, and then of course you have to drive it with one of the many choices for flyback circuits.
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WTB: High Voltage 60Hz Transformer
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