Is there such a thing as a high voltage polarity switch, what's it called?

Question

I'm just wondering, I need something than can switch polarity frequently and automatically in a high voltage circuit. Is there such a device? What is it called and where can I get one?

Answer 1

It would really help if you defined "frequently" and "high voltage", also the power level involved would be important to know.

If "frequently" is a few times a minute, various sorts of mechanical switches could be used, even up to rather high voltages if sufficient clearances are used.

If "high voltage" is only a few hundred volts, then perhaps a relatively simple solid state  "H-bridge" could be used which could work up to fairly high frequency.

If frequency and voltage are high it gets harder, especially at high power levels, but it can be done, HVDC transmission lines are used for hundreds of megawatts at hundreds of kilo-volts, and the polarity is changed 50 or 60 times a second at the receiving station.

Answer 2

High Current MOSFET Polarity Switch

The synchrotron community utilizes high magnetic field manipulators called Undulators to generate high intensity X-rays from intense electron beams. Rows of precisely positioned magnets create a sinusoidal magnetic field that causes the electron beam to undulate, which produces the desired X-rays. The intense magnetic field, nearly 1 Tesla, is further shaped by electro-magnetic correction coils mounted to the undulator, in order to direct and influence the shape of the X-ray beam. These correction coils typically carry high DC currents, up to 50 amps, but at low voltages.

The direction of the current in the correction coil must be reversible to allow the greatest influence on the magnetic field. Power supplies with reversible polarity are not commonly available. The high currents coupled with the need to reverse current direction (polarity) leads to a design problem. Most contactors that can carry such currents are usually large, expensive, and electrically noisy (to actuate) because they are designed to interrupt high voltages as well. The correction coils are typically driven by low DC voltages between 10-24 volts. Servo amplifiers have been used in the past to reverse the current flow in correction coils but while these can control current precisely, the voltage is quite variable which can affect the total power delivered to the coil. Custom power supplies have been designed (by Agilent) with reversible outputs but these are expensive and require PC communications.

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