A colleague of mine needs a high voltage supply that can be operated in such a way that the output will follow a sine wave in the frequency range of 50Hz to 1MHz (roughly) and a potential of 6kV.
There will be two plates that the supply is connected to, and the idea is to have the direction of the potential between the two plates rapidly switching. The application is related to a research project that I don't know too much about.
Any pointers are greatly appreciated. If it's any help, they already have high voltage supplies in the lab, but I don't know if there's any easy way to convert this into oscillating output.
Using a transformer to generate 6kV is not easy, but I think up to a few kHz should be possible with ferrite core transformers. But it might not be a perfect sine wave. Is higher frequency components a problem ?
The 1MHz requires very specific knowledge.
What is the current ? Perhaps 1mA or less ?
I hope you do this in a high voltage lab that is completely shielded for radio waves. Use a long wire, and a little modulation, and perhaps you can cross the ocean with the radio waves.
I thought it seemed a little absurd as well. I do know currents are probably less than a 1 mA.
I am thinking the specs he gave me were probably not completely accurate and I'll ask him to forward me the paper he was referring to before getting my feet too deep into this.
I never even thought about the radio waves that would be produced...
I know from experience that this particular task is actually extremely difficult to accomplish, especially at the frequency range you are discussing. Look into Tesla Coils and good luck. If you can figure out a way to do this safely and consistently please share!
Agreed that the frequency range is a major problem. At audio frequencies 6 kV is not hard (you can buy neon sign power supplies that put out 10 mA @ 2 kV @ 20 kHz for $5) but at 1 MHz, very difficult.
Okay. I was working with the specs he gave me, but after reading the papers, I think he may have misspoken.
The actual range of frequencies I need are no greater than 5kHz.
The original authors used a setup that had a square wave function generator as the AC, and a high voltage DC source that had a bias, or offset option. I'm not too sure I understand what that means, other than that the resulting output is a high voltage DC source.
A high voltage DC is not hard.
I think the bias or offset is some kind of tuning of the circuit or transformer, or the circuit itself. Perhaps they wanted to explain the voltage multiplier, which uses offset added to offset added to offset. The great think about it is, that with diodes of only 1kV it is possible to make 6kV.
The 5kHz is a lot better, that is well within the audio range.
An alternating high voltage can be done with transformers.
Transformers in microwave ovens, or for neon lights, or from old analog TVs, or car ignition coil or a Tesla Coil can do that.
Transformers that are made for higher frequencies are not hard to find, but they can't do low frequencies. Perhaps you need two or more transformers, each for a specific frequency range.
Did you know it is very hard to make a precise voltage with high voltages ? When it is measured with a voltage meter that has 10M or 100M input impedance, the voltage drops a lot (maybe to half the voltage). And after the meter is disconnected the voltage rises again.
The video below is a lot of fun, but I don't know if it can do low frequencies and how controllable the voltage is. I'm also not sure if all Tesla coils make good balanced alternating sinus waves.
Tesla coils don't, but its a good place to start to learn. You'll need to learn spice modelling as well. It will help immensely to see if what you build will react as you expect. Or you can look online. Also, depending on the situation, your currents could end up being quite high in places, especially at a low duty cycle. And you need to be careful about arc-overs.
