Protection system for parallel circuit oscillating inverter - triggers both thyristors in half of rectifier bridge if frequency of current in parallel capacitor too low

摘要

The device protects parallel circuit oscillating inverters with power output, for example as used in induction furnaces. If the charge or the inductor (11) is defective the oscillating frequency departs from normal and may damage the rectifier bridge (1, 2, 3, 4). To detect this the frequency of the current in the parallel capacitor (12) is measured and compared with a reference valve. If less than this limiting value triggering of both thyristors (1, 2) in half of the rectifier bridge is initiated. The load circuit is thus bypassed and the voltages and current acting on the inverter brought within known values.