transformer secondary coupling

You can probably get lots of ferrite-cored parts surplus, and then rewind as needed. There are also magnetics distributors like Magnetics, Inc. that can get you samples of nearly anything they carry.

Jon

You could take several single winding 4 connection autotransformers and 'stack' them. Say with 5, each one would only 'see' 10kV each.

"Jon Elson" Jamie Moron : Phil Allison

** That was not my reasoning.

The OP is clearly a clueless, trolling idiot with a death wish.

His motives for wanting such a supply are deeply suspicious and he has not one tiny clue of the safety or design issues involved in such high voltages.

Shame here on anyone who assists his lunacy.

.... Phil

Hi Phil,

I've made a handwound tesla coil before so try to be careful around HV. The purpose of the power supply is for an electron beam melter/welder.

cheers, Jamie

Hi,

Thanks that is interesting and could allow using smaller standard ferrite cores instead of a custom large toroid core. How would the efficiency of five stacked autotransformers compare to a single transformer? I'm not sure about driving the autotransformers though, I guess there would need to be extra floating HV supplies to drive them.

cheers, Jamie

Jamie Moron :

** Thought you must be one of THOSE NUT CASES !!

** You must be utterly INSANE !!!

Piss off - bloody imbecile !!!!!!!!!!!!!!!!!!

Magnetic "lines of force" are closed loops. Spacing between magnetic parts (iron, silicon steel laminations, ferrite toroids, ferrite E-cores, bobbins, etc) and non-magnetic parts (the copper wires, insulation, air) are not relevant. Turns for "secondary" and turns for the "primary" all act the same when they are coupled by the enclosing magnetic parts. The turns ratio, etc is all the same no matter how they are interleaved. Above is first-order; leakage inductance, etc are second-order terms and are usually small enough to be ignored or almost ignored. Working from inside out, either put HV stuff inside first - with the result that insulation of wires from turns going out must protect the overlaying LV turns that would crowd into the exiting leads, OR put the LV stuff inside first - with the result that insulation of wires from turns going out must be protected from the overlaying HV turns that would crowd into the exiting leads. OR..LV layer, HV layer, LV layer, etc. OR..multifilar HV and LV side-by-side. Pick your poison.

ce

ng

ind

c.

No need for 'extras'

simply drive the coil at GND potential and the voltage multiplies up to 50kV using four autotransfomers with four connections like such: d- . c . . . . b . a

first transformer GND a, drive b. at d you have 10kV

2nd transformer connect a2 to c1 and b2 to d1, at d2 you have 20kV

3rd transformer connect a3 to c2 and b3 to d2, at d3 you have 30kV

and so on, until at d5 you have 50kV

*IF* you build the structure properly, you will even have controlled gradients that will handle the inevitable discharges WITHOUT catastrophic failures. Just envision how a diode stack is constructed using rings.

If the efficiency of your transfomer is 98%, then you have an overall efficiency of 90% only 150watts, HOT!

99% you have 95% and only 75 Watts still HOT can you build your transformers to have 99.5% efficiency? then you're talking about 37 watts, not so bad.

Remember therule of thumb for heat in still air

1 C rise for every watt being dissipated over 100 sqin.

If your structure has 100 sqin of 'good' surface, we're talking 40C rise above ambient, not bad, but not good either.

Oh, did you want DC at 50kV to supply 1500w? then good luck. Can't even imagine the diode stack to do that! From memory diode stacks are lucky to be 70-80% efficient. but it is doable. You can stack commercial DC supplies *IF* you do it carefully.

or make your own, probably a 7 ring stack would compromise well.

The efficiency goes to hell as you try to use unmatched components and MUST add balancing circuitry else a discharge will....just say it's dramatic.

To increase efficiency, you could add some complexity, drive high voltage components to act like diodes, that exhibit extremely low Von. But we're talking complexity.

Hi,

Thanks, would vacuum tube diodes work at 10kHz+ and 50kV/50mA?

I am using a vacuum chamber so maybe could put thermionic diodes in a full bridge configuration right in it?! :)

cheers, Jamie

Early color TVs used a thermionic diode as a half-wave rectifier with half-sine pulses >25kV, about 20 microseconds wide at a PRF of 15.75kHz. About a milliamp DC out. Directly heated filament, supplied from a well-insulated few turns loosely around a flyback transformer limb.

I doubt anybody makes them, now. Somebody like Perkin Elmer might still make similar diodes to special order, at megabux.

If you only want a few, swap meets might be the best bet. I can't recall the tube number, but I bet Mike (Terrell) can.

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

1B3 & 3A3 were the most common. 3AW3 & 3B2 are a couple of the others. I have 23 new 3A3 on hand if anyone wants some. 5 are GE branded, 18 are Westinghouse branded.

--
You can't have a sense of humor, if you have no sense.

How are you thinking to avoid being grilled by X-rays? Even the tube rectifiers generate an appreciable amount of X-rays at those voltage and power levels.

--

Tauno Voipio

In the old color TV sets, the diodes were in a metal box, both to keep the 30kV away and to contain the X-rays.

How about taking the easy route and get some *old style neon sign transformers. I think a standard rating was 15kv at 30ma, so it may take series/parallel combo to get to 50kv at 50ma. I'll let you pick the rectifiers. I ran a couple in series one time and had sparks coming out of the ground, yikes! Mikek

The high voltage secondary on a NST is center tapped and grounded to the case.

You could use a full wave CW multiplier.

Hi,

Is it practical to make a HV fullwave rectifier with 4 thermionic diodes? I'm not sure how the filament heating supplies would work due to the floating voltages.

cheers, Jamie

The cathodes are connected to the filament, so you would need four isolated filament supplies with insulation rated for the voltage. On TVs they used a piece of second anode wire an a turn or two wrapped around the flyback core.

--
You can't have a sense of humor, if you have no sense.

They'd need isolation, one could be on each end of the main HV winding, but for the positive rectifiers you'd need a fully isolated supply ____ . . . . . . ::(__ `--------------------------+-----. |_____ ::(_ `----------------------------|-----' | . | ::(_ | . . . . . . | ::(_ . . . . . . | | ::(_ .-------------. |______| | __ ::(_ | .----------' | . | 3::(_ | | . . . . . . | 3::(_ | |(+) (-)| 3::(_ | | . . . . . . | __3::(_ +--|----------. |_____ | ::(_ | +----------' | . | | ::(____|__|____ . . . . . . | | ::(____|__|__ | | . . . . . . | :: ____| | | `-----------------|-----. |______| ::(_______| `-------------------+-----' | . . . . . . .

--
?? 100% natural

--- Posted via news://freenews.netfront.net/ - Complaints to news@netfront.net

No -- you really want a doubler. The reason most TVs go half-wave is because the positive and negative pulses are asymmetrical, so where the positive peak is 20kV, you only gain maybe 1kV grabbing the negative peak (which is when the sweep tube / HOT is conducting), not worth installing another diode to make a doubler. (Triplers and quadruplers have been variously popular, however.)

Your PSU will work best with a 50% duty cycle into a doubler, since that maximizes magnetic capacity, conduction angle and minimizes components and voltage drops.

Doublers are also quite tolerant of leakage inductance (which you will inevitably have in ample supply) and work well on resonant circuits (where the peaks are symmetrical, even if the conduction angle isn't as high as a square wave's).

FYI, you can purchase rectifier stacks from Surplus Sales. Voltage drop is much less than vacuum style, though switching losses compensate a bit. They are often specified for oil submersion service.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms