RELIABLE HIGH-POWER SCR CONTROLLER DESIGN

Common practice in the design of zero-crossing detectors and gate drivers for low-power SCR's falls far short of reliable industrial practice when applied to high-power designs. Experience with controllers that supply thousands of amperes at 240 and 480 volts has led to designs that protect the expensive silicon controlled rectifiers without fuses, and to circuits that find the true zero-crossings despite jagged and noisy line waveforms. Guidelines for the design of correct timing, electronic fusing, self-monitoring and for gating the SCR are presented.