High frequency, high voltage transformer

Your specs (200W, 7:1 voltage ratio, AF to supersonic frequency range) are most similar to a VERY LARGE audio output transformer.

It may also be described as a "modulation transformer".

One very strange thing for a switching supply is your large desired range of operating frequencies. Your range doesn't exactly match up with audio output transformers but it's only off by a factor of 2 or 3. If you try to run a typical audio transformer up that high you'll probably be hitting a resonance of some kind (which may in fact be desirable for your operation, I dunno!!!)

If you can aim for a substantially lower fixed frequency, you may find a circa 400Hz unit commercially.

Hint about sizing transformers: TV flybacks and ignition transformers are certainly not in the 200W class you're aiming for.

If you want circa 2-3kV DC at in the 200W range, there are MUCH easier ways of doing this that are straight out of a textbook or ARRL handbook.

Tim.

Is this a power supply or some other application, the 1khz is very low for a smps. otherwise wouldnt be too hard to do from stocked E cores or from say a scrap pc power supply. some cores wich arnt glued come apart ok. air core will be a bit large.

You just need to follow the formulea wich gives number of turns based on cross sectional area of ferrite and frequency, number of Turns N, Core cross sectional area A (m^2) RMS Voltage V, and Saturation flux density B (use 0.15 to 0.2 Tesla for most ferrites) :

V = 4.44.F.N.A.B

wire diameter to give a reasonable amps/sq cm.

You can seriously kill yourself with this voltage/current though.

Colin =^.^=

I haven't gotten into scavenging household electronics, as some have, but except for the primary center tap, those 'pecs look much like a microwave-oven transformer. Look up half-bridge and H-bridge driving circuits to see why a center-tapped transformer isn't necessary or wise.

--
 Thanks,
    - Win

Why? What is it supposed to do?

Hi all,

Its a small experiment on electrolyzing water.

I want to apply 2kV AC across two plates and measure the HHO output with frequency in the range 1kHz to 50kHz. (I'm expecting a peak around

20~30kHz)

Thanks, Harshana

PS: Now don't mark me as one of those people who's experimenting on over unity gadgets. I just want to get the frequency response on HHO output for specific voltages.

Harshana wrote:

Hi all,

Its a small experiment on electrolyzing water.

I want to apply 2kV AC across two plates and measure the HHO output with frequency in the range 1kHz to 50kHz. (I'm expecting a peak around

20~30kHz)

Thanks, Harshana

PS: Now don't mark me as one of those people who's experimenting on over unity gadgets. I just want to get the frequency response on HHO output for specific voltages.

Harshana wrote:

200W (well 200VA)

200W air core at only 50kHz ???

too high in voltage, maybe too little power handling capacity (one from a

36" crt might be big enough), but the design frequency 17kHz is about right

nowhere near enough power handling capacity.

maybe something from a PC powersupply, but you'd need to modify the secondary...

AIUI they run the primary at around 300V

Bye. Jasen

Based on what evidence, do you have any references, etc. for us to read?

BTW, I still think your best bet is two MOSFETs or IGBTs in a half-bridge driving an old microwave-oven transformer. In fact, you can probably use the oven's AC-power wiring and rectifier, etc. There's a lot of detail on the web.

--
 Thanks,
    - Win

You might be able to use an ordinary mains transformer in reverse, as the min frequency is 20 times higher than line freq you can use 20 times the voltage, or to be conservative 10 times therefore a 240v primary can be used as your

2kv secondary, you can chose whatever secondary to use for you primary eg 24-0-24, for 200vac input, current ratings will remain unchanged, therefore power rating will be increased by a factor of 10, although the higher frequency may cuase more heating, a 20watt transformer is quite small.

Colin =^.^=

Hello Win,

Maybe this shows my age now but when I took apart our first microwave the transformer was a big old 50/60Hz laminate core. Whenever I tried to use power transformers at higher frequencies their performance became rather lousay above a few kHz.

If the new microwaves use switchers those transformers probably won't work at 1kHz.

--
Regards, Joerg

http://www.analogconsultants.com

Lousy, yes, but how lousy? I think the o.p. can stand some losses for his electrolysis experiment. If not, he can let us know how it works out.

Yes. How many old defective microwave ovens do you think have those? I'm pretty sure my 14-year-old model doesn't.

--
 Thanks,
    - Win

Hello Win,

Maybe it works. When I was a kid I sometimes used small line transformers to replace a blown audio transformer in a tube final. Worked ok but not great. Later when I had some more gear I measured one and it was completely flat above 10kHz. Then I knew why FM stations sounded so dull after such "repairs".

It's surprising what people toss these days just because the decor or something doesn't fit. A neighbor chucked a perfectly good TV set that wasn't even 5 years old because the power cord had gotten whacked during a move.

--
Regards, Joerg

http://www.analogconsultants.com

the insulation might not last real long with that sort of abuse.

Bye. Jasen

On 28 Sep 2006 11:27:26 GMT, jasen Gave us:

The bigger question is what is the application. I'd like to know just what he thinks he needs 100mA for.

You want a ferrite core. You want around 57kHz.

Also, after generation at the transformer secondary, one needs rectification and storage to make DC, as well as current limiting and arc suppression considerations.

If it is simply AC output that is desired, a lower frequency and other than ferrite could be used. Again, however, it depends on the application involved.

On 28 Sep 2006 04:44:53 -0700, Winfield Hill Gave us:

Excellent suggestion. A pair of FETs and an oscillator setup makes a fine input stage driver (though not likely at 300 Volts). Likely nice and cheap cost wise as well. The transformer you suggest is a bit overkill though for his needs in both size and capacity, but it would have the isolation and would function properly.