I'm trying to automate a small Thermal Dynamics 35 amp plasma cutter with 12kV pilot arc starter. I've built a THC based on Tom Caudle’s design. I'm having problems with interference on the scaled voltage output during arc starting and pilot arc. I have diodes on the voltage divider input and low-pass filters on the output. I'm getting spikes that make my Fluke meter do strange things. As soon as the the arc transfers to the work, the high voltage starting circuit shuts off and my scaled output voltage stabilizes to normal level.
Any suggestions Tom?
Does the THC300 work on HV/HF machines?
Jon