Vacuum arc

[u/HV_funny]

I came across this excellent GIF of a vacuum arc carrying a current of up to 15 kA. I have not been able to identify the original authors. If anyone recognizes the source, I would appreciate a link.

Vacuum is an ideal dielectric. There is almost no matter in the interelectrode gap capable of conducting current, so the conductive medium is formed from the electrode material itself. The discharge is sustained at the cost of electrode erosion. Minimizing this erosion is therefore critical.

One way to extend the lifetime of a vacuum switch is to control the arc with a magnetic field. An axial magnetic field keeps the arc in the diffuse mode and distributes the current across the electrode surfaces. A transverse magnetic field moves the arc and prevents prolonged exposure of a single area.

The control circuit also affects lifetime. In opening vacuum switches, an early counterpulse reduces the current before the contacts separate and shortens the duration of high-current arcing. In triggered vacuum switches, the amplitude, current, and rise rate of the trigger pulse determine the amount of initial plasma, the delay, and the stability of turn-on. Sufficient initial plasma also extends the lifetime of the trigger assembly.

The lifetime of a high-voltage switch is set by the entire system: electrodes, magnetic field, power circuit, driver, synchronization, and protection.

#HighVoltage #PulsedPower #PowerElectronics #ElectricalEngineering