Gould Inc.

I-t-e Imperial Corporation

Peter Pang

Lee A Davis

The primary winding of a saturable transformer, coupled to an a.c. circuit, drives the core of the transformer into saturation during at least a portion of the cycle of an a.c. current flowing through the circuit. A plurality of rise-time indicator pulses, having a duration inversely proportional to the rate of rise of the a.c. current being monitored, is induced in the secondary winding of the saturable transformer. The rise-time indicator pulses appearing in the secondary winding of the saturable transformer are applied to a pick-up circuit which generates a plurality of rectangular pulses whenever the a.c. current exceeds the normal rated value of the circuit. The pulses generated by the pick-up circuit each have a duty cycle inversely proportional to the rate of rise of the a.c. current being monitored. An inverter circuit, responsive to the pulses generated by the pick-up circuit, generates a second series of rectangular pulses having a duty cycle proportional to the rate of rise of the a.c. current being monitored. The second series of pulses are applied to a tripping circuit which monitors the duty cycles of these pulses and interrupts a.c. current flow in said circuit after a time delay which is inversely proportional to the magnitude of the a.c. current being monitored.

Solid state tripping circuit

A solid state tripping circuit for sensing overcurrent conditions in a circuit connecting a power source to a load circuit and for controlling the operation of a circuit breaker in series in the circuit. The tripping circuit is responsive to different levels of current flow in the protected circuit to actuate the circuit breaker to the open condition after a variable time delay. The duration of the delay time is a function of the ratio of the overcurrent sensed to the rated circuit current. Energy for operation of the tripping circuit is supplied directly by the sensing circuit to eliminate a separate power supply.

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Hong Kong, China

Peter Pang