One recommendation is the requirement of having "2" separate operations to turn on high voltage; this requires at a minimum a Main Disconnect (Lockable Safety Switch) and a start-stop push-button station with seal in contactor. This requirement supports my contention you should never "instant on" high voltage equipment. YMMV, but I've seen catastrophic, spectacular failures doing this.
I built this into my controller. After the main set of breakers at 20A comes 1 30 amp relay before the variac and 1 after. The first is controlled by the HV Enable PB/relay and the second by the Fire/Fire Latch PB/Key switch and relay. E-stop will kill all but the Fire Latch, and Fire Latch must be returned to Off before restart can occur. Since the latch keeps the second relay closed, I had to make it so that it must be turned off on a restart to prevent the HV going active when HV Enable was pressed. But before you can access the HV Enable, you have to turn the momentary keyswitch to the start position, and select gap and/or start the rotory.
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