Abstract: The circuit breaker comprises a thermistor located in a cold zone, near the front face of the trip device and at least one thermistor located in a hot zone, at the bottom of the circuit breaker case, in proximity to the circuit breaker connection terminals. The temperature difference measured between the hot and cold zones is representative of the temperature rise of the system protected by the circuit breaker and is used to modify the time delay of a delayed tripping function when the circuit breaker closes. The trip device can also take into account the temperature difference existing at the time of the previous trip.

Abstract: The protection device ocmprises automatic commutating means interposed between the base of a transistor to be protected and the collector of a power device to cause a flow of current having a low voltage drop between the base and the collector when the collector voltage falls below a predetermined value.

Abstract: In a drive control apparatus for an electric actuator to be activated under control of a changeover switch, the drive control apparatus including a power transistor arranged to supply therethrough the power to the electric actuator from an electric power source in response to operation of the changeover switch, a presumptive temperature of the power transistor is previously memorized and renewed in consideration with an increment of temperature change caused by consumption of the power when the electric actuator has been activated. The presumptive temperature is further renewed in consideration with a decrement of temperature change caused by lapse of time after the electric actuator has been deactivated. The power supply to the electric actuator is permitted only when the presumptive temperature is lower than a predetermined value. When the presumptive temperature becomes higher than the predetermined value, the power supply to the electric actuator is prohibited.

Abstract: A current interrupting apparatus adapted to be interposed in either a single or multiple phase electrical circuit includes a fuse interposed in each phase of the circuit. A current interrupter is electrically connected in series with each fuse for interrupting the current through the circuit, each current interrupter including a pair of normally closed electrical contacts and structure for opening the pair of contacts in response to a fault current of a magnitude different from the magnitude of current necessary to cause fusing of the fusible element of the fuse. A current interrupter triggering circuit is included in the apparatus for triggering operation of the contact opening structure of all of the current interrupters in response to fusing of the fusible element of any of the fuses to protect the circuit from the effects of single phasing.