Abstract: A safety circuit for a silicon controlled rectifier controller of the type wherein the current delivered to a load is determined by controlling the firing angle of the silicon controlled rectifiers. The safety circuit is capable of sensing a shorted condition in the silicon controlled rectifiers and automatically disconnecting the load from the AC mains in the event of such a short circuit condition. Load current is sampled at a time in the cycle where it is expected to be zero. If at the sampling time a non-zero condition is detected, a relay is made to operate to actuate a circuit breaker or to perform other desired functions.

Abstract: A frequency inverter using thyristor(s), wherein a gate circuit produces both positive triggering signals and negative reverse-bias signals by utilizing outputs of the timer in order not to fail turnings of the thyristor, and the timing of both signals are automatically controlled to by synchronized with oscillation of the resonance circuit connected to the anode and the cathode of the thyristor, so as to respond to a change of load condition, so that always suitable triggering signals and reverse-bias signals are applied to the gate of the thyristor.

Abstract: A system for and a method of extracting energy from a capacitive source, for example the energy induced in an insulated section of the overhead wire of an AC transmission line. The energy is extracted from the overhead wire by tapping the primary winding of a voltage step-down transformer which develops at its secondary an AC voltage the value of which is regulated through shunt switching. The shunt switching regulation as such is achieved by power thyristors the firing of which is selectively controlled in accordance with the phase and the amplitude of the output voltage. A comparator is used to compare the output voltage value with that of a signal delivered by an internal ramp generator. Moreover, the firing instant of the thyristors is governed by the output signal of the comparator and also in function of the information on the polarity of the output voltage cycles.