These are some shots of my control cabinet I've put together for 120V operation.

This is the heart of it, a General Radio W30 120V 30amp Variac.

This is the controller box. The frame is made from 3/4" square tube and it measures approx. 18" x 18" x 15". My friend Don put it together to play with his new welder. I've covered it with 1/8" smoked Plexiglas. Once I have it completed, I'll remove the masking paper from the Plexiglas. The legs with wheels were recovered from a microwave oven cart that was being disposed of. The legs are made of 12" square tube which fits nicely inside the 3/4" square tube frame.

It contains the 30amp Variac, a 30 amp contacter with a 24VAC coil, a 24VAC transformer. On the top of the controller box, there is the main power switch, a key switch, a green indicator lamp and a momentary push button switch. The key switch becomes operable when the main switch power is turned on.
The main power switch feeds 110VAC to a 24VAC transformer, which engages a relay that feeds 110v to the outlet that the spark gap plugs into. It also feeds 24VAC to the key switch. When the key switch is turned the momentary push button switch becomes active and the green indicator lamp comes on.
When the push button switch is pressed, the contactor is supplied with 24VAC and closes, which supplies power to the Variac. The Variac feeds it's output through a 20A Corcom EMI filter which is hooked to an outlet. This outlet is what the HV transformers connect to.

Metering done by is a 0-50AAC and a 0-200 DC microamp Simpson meters. I have a rectifier and resistor network setup so the microamp meter now reads voltage. 0-200VAC.

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