GB428357A - An improved protective circuit arrangement for installations comprising a remotely controlled automatic electric switch - Google Patents

Abstract

428,357. Protective cut-out arrangements. SHEVLIN, J. T., 15, South Street, Finsbury, London.-(Siemens-Schuckertwerke Akt.-Ges.; Siemensstadt, Berlin) Jan. 24, 1935, No. 2425. [Class 38 (v)] In a protective arrangement for installations comprising an automatic circuit-breaker 8 operatively associated with an earth leakage relay 13 and controllable from a remote control position over a cable 5 containing a control line 17 and earth line 18, more particularly for controlling the motor 6 of a coal-cutting machine, an earth relay coil 22 provided at the control position is responsive to a short-circuit between the control line and earth line, and on such response establishes an earth circuit through a limiting resistance 24 from one of the supply lines of the installation, and thereby operates the earth leakage relay 13 to open the circuit-breaker 8. In the arrangement shown, the relay 22 is directly connected in the control line 17 which also includes the contacts of the relay 13, a no-volt coil 11 and the secondary winding of a transformer 9 energized from the supply. If the main switch 7 is closed, closure of a button 25 energizes a starting relay 12 connected in parallel with the no-volt coil 11. The relay 12 in turn closes the circuit of the operating winding 10 of the circuitbreaker 8 ; the latter thereupon closes and is held closed by a latch as long as the no-volt coil 11 is energized. The winding of the earth leakage relay 13 is connected to an artificial neutral point formed by three resistances or capacities 14, 15, 16 connected in star to the motor supply conductors, the arrangement being such that if the relay is energized the connection between the control line and the no-volt coil 11 is interrupted and the circuitbreaker 8 is released. In the event of a short circuit between the control line 17 and earth line 18, the coil 22 is de-energized, and one of the supply conductors is connected to earth through the resistance 24. The resulting displacement of the neutral point causes the earth leakage relay to respond, with consequent opening of the circuit-breaker 8. The latter may be opened at any time by depressing a button 26 to interrupt the circuit through the control line 17.