GB1432715A - Switching systems - Google Patents

Abstract

1432715 Switching systems for electric motors EICKHOFF MASCHINENFABRIK U EISENGIESSEREI mbH Gebr 20 Sept 1974 [11 Oct 1973] 41006/74 Heading H2J A switching apparatus comprises a first relay 6 for operating a switch 3, 2 for connecting a motor 1 to a power source RST, first and second rotary switches, hereafter called cut-out and cut-in 8, and a switch 7 in series with the first relay 6, a second relay 13 for operating the switch 7, a circuit for bridging the cut-in 8 and the switch 7, and a locking device 12 for coupling the cut-in 8 and the second relay 13 and arranged so that when the cut-in is closed to position II and the second relay 13 has been energized, this relay is mechanically held in its energized position in which the switch 7 is open. The apparatus is preferably a part of a sharerloader coal-mining machine. In operation cut-in 8 is moved to position II and cut-out, which is coupled, also moves to its position II, and relays 6, 13 are both energized, relay 13 after a delay. Switches 2, 3 are closed and the motor is energized. After the delay, energization of relay 13 opens switch 7. Cut-in 8 and cut-out 9 move back to position I under a spring bias control, and relays 6, 13 remain energized via the bridging circuit since switch 3 is closed. If cut-out 9 is moved to position 9 or emergency switch 10 is pressed, the motor 1 is stopped. If the emergency switch 10 is pressed and the cutin 8 is jammed in position II, since in these circumstances the locking device 12 maintains, via relay 13, the switch 7 open, the motor 1 will not be restarted when the switch 10 remakes the circuit in line 5. In a modification, Fig. 2 (not shown), a transistor device is in series with the relay 6 is provided and is only turned on when current is present in the main circuit including the cut-in device.