The high-frequency operation of GTO's (gate turn-off thyristors) in parallel inverters with resonant load for induction heating is investigated. The load-forced turn-off process of devices with reverse-blocking capability is analyzed on the basis of experimental results. The behavior of anode and gate voltages and currents during turn-off and during reapplication of forward voltage is analyzed considering various operating parameters (rate of decrease of anode current, rate of rise of anode voltage, reverse-bias amplitude and duration), and in particular gate-command timing. Appreciable benefits in terms of commutation losses, turn-off time, and snubber reduction are obtained as compared with the usual performance with chopper operation. Indications for an optimal gate-control strategy are also given.
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