How do you control an Silicon controlled rectifier with a potentiometer in a variable high amperage circuit?

Hi! I'm trying to build a constant voltage variable high amperage circuit. I know that you can use a silicon controlled rectifier in inverse parallel to conduct the full waveform in AC. How can you use a potentiometer send the signal to the SCR without blowing up the small potentiometers available (circuit will be up to 200 amps.) Thanks to anybody who can shed some light on this!|||One approach is to use pulse transformers to transmit the gate pulses from the triggering circuit to the SCRs. Another approach is to build a separate transformer-isolated power supply for each gate driver circuit and use optical couplers to transmit signals to the gate drivers. A third approach would be to use light-triggered SCRs, but I don鈥檛 know about the availability of those devices. With any approach, you could reduce the complexity by using triacs instead of SCRs.