Transformers

You need AC for a passive transformer to work (actually you need a magnetic field that changes over time). DC voltage cannot be transformed by a passive transformer. You have to chop it up, transform the chopped up waveform, and then smooth it out again. In other words it takes an active circuit.

So are they different? Yes in that a DC transformer doesn't really exist.

Charles Perry P.E.

In that case, do they make bridge rectifiers for 2000+ volts AC?

I have seen adjustable speed drives at 4000 volts so I would assume they do.

Charles Perry P.E.

How does 32,000 volt bridge sound to you?

transformer?

Please give us a few simple clues about what you really want then maybe we could properly answer your question.

I have a transformer from a microwave oven and I want the output DC

What are you going to do with the DC - aside from possibly killing yourself? My fear is that you may not recognize the dangers or know how to work with high voltage safely.

Sorry Chuck you are wrong on that one. DC transformers do exist and they are used in most satelites. They use two cores and require an energizing source and are used to measure DC currents. They are some times refered to as Mag Amps. You will find them explained in Rotors.

I also invented a dc transformer which is extremely accurate some years ago. I can acturally measure with an accuracy of about 1 part per million or even more. The higher the current, the more accureate it is. The offset is fixed, no matter what the current is. I delivered a paper on it at the IEEE but it was a bit advanced and I do not think any one even understood what was going on. It uses a single core. Basically the DC drives a very narrow loop material way into saturation. I mean like a thousand times the width of the hysterieses loop. Now a voltage is applied to the search coil so as to bring the core out of saturation. When the core comes out of saturation and the core travels back up the loop there is a voltage pulse out of the sense loop. This pulse then is a measure of how deeply into saturation the core was and a measurement of the current flowing. Because the saturated state of the core is so large compared to the loop width, the measurement can be very accurate. I actually build and tested the device.

Advantage is just one core and extreme accuracy.

Yes - I've seen ones up to around 500kV (they call them HVDC links, but they are probably a little outside your price range... :-)

Not really. I said there were no passive transformers. Magamps are active.

Also, he is trying to transform DC for power use, not measurement.

Charles Perry P.E.

I'm gpoing to use it to charge capacitor banks

I'm going to use it to charge capacitor banks

Sounds like a potentially lethal device.

Dave

...

Interesting sounding invention, except that it is a measuring device and not a DC transformer. A DC transformer would convert a DC voltage/current to a different DC voltage/current.

I misunderstood. I thought he wanted to measure the current. In any case, these magamps are called DC transformers even though they are just for measurements.

That is even more dangerous. Do you know any thing about HV. Do you know how far a spark can jump. Do you understand the effect of a sharp point on the high voltage end. In any case, work with one hand in your pocket if you will not be disswaded.

If you have to ask questions about HV DC that means you do not have enough knowledge to work with it. Nothing substitutes for a couple of years of apprenticship where you learn the things not in the books.

I have a 5000 volt meter. It is a direct reading meter and is not an electronic one. It reads 5000 volts directly and does not require any special probes. The interesting thing about it is that if the conditions are right the needle sticks to the glass.

I used it when I was designing 28 to 5000 volt isolated, regulated, power supplies that could fit into a 20 cigarette package.

So now you can die by direct electrocution or when one of the caps explodes.

If you are unfamiliar with the specifications for HV rectifiers, what makes you believe that you know what you are doing with caps?

in article snipped-for-privacy@uni-berlin.de, Charles Perry at snipped-for-privacy@hotmail.com wrote on 9/17/04 5:16 AM:

There is a fundamental problem to assigning passive or active attributes to a device. To me, there is nothing active about a silicon diode sitting on the table. Nevertheless, by driving it with an ac signal, it can become a parametric oscillator. By driving a tunnel (Esaki) diode with dc, it can do all kinds of interesting things.

Devices do not produce energy although they do transform it.

The main distinction should be between linear and nonlinear devices.

Bill