Commutating oscillator and current-limiter for solid state switching circuits

摘要

A circuit for use in a silicon controlled rectifier (SCR) control for direct current powered loads wherein the commutating voltage on the commutating capacitor is used to generate a gate pulse for the commutating SCR to thereby turn the main SCR off at a fixed and predetermined time after it has been turned on. The commutating voltage in the commutating capacitor is also monitored during charging thereof and the gate pulse for the commutating SCR is generated prior to the predetermined time in case the peak current through the main SCR reaches a predetermined excessive value. The gate pulse is also generated prior to the predetermined time during plugging or low-speed operation of motors.