Electronic crowbar for AC or DC lines

For forward protection of electronic equipment, this circuit is used to prevent exceeding the supply voltage. Because of improper switching, wiring, short-circuiting, or regulation failure, the electronic crowbar circuit can quickly place a short on the power line and then pass the protection device to lower the voltage to near zero. Two-way thyristors and SBS have bilateral devices, and this circuit is useful on DC AC power lines. The value of the resistor can be varied to cover different ranges of the supply voltage.