Multipoint electrical emergency trip for mining applications - has trip circuit supervision and remote indication of emergency switch operation

摘要

The trip circuit comprises an interface unit connected to an electrical supply and to trip relays which also generate a d.c. trip circuit supply. The trip switch circuit is connected through the various operating switches to a terminal unit. The terminal unit generates a high frequency signal which is detected at the interface to prove electrical continuity of the conductors. A trip is initiated by operating one of the switches. A supervisory unit monitors the impedance of the trip circuit. Operating a switch closes a circuit of a defined impedance which is measured and employed to bring up an appropriate indicating lamp at a supervisory station. The impedances are typically set by connecting diodes in series. The diodes may be directly in one line or in the connector between the normally open terminal of the switch and the opposite pole of the trip circuit.