GB145072A - Improvements in and relating to the suppression of sparking at the interruption of conductors traversed by a current - Google Patents

Abstract

145,072. Siemens - Schuckertwerke. July 29, 1915, [Convention date]. Sparking, preventing.-A counter electromotive force, impressed upon the circuit at the moment of interruption, is produced by an electro-dynamic appliance such as a coil with a movable iron core or a suitably-connected dynamo-electric machine. In the simplest form, shown in Fig. 1, a coil b connected in the circuit to be interrupted attracts an iron core c attached to the movable member c of the switch a. When a latch d is released, the switch is pulled open and during the movement a counter electromotive force is generated in the coil b which partly neutralizes the sparking effect. Fig. 2 shows an arrangement having a series-wound direct-current motor f adapted to open the switch through mechanical gearing g, h upon the release of a latch d. The back electromotive force of the motor provides the compensating effect. The geared member h may be arranged to operate the switch lever by impact after the motor has travelled through a certain distance, so as to get an adjustable counter effect. The arrangement shown in Fig. 3 employs an independently-excited motor f of which the armature is normally short-circuited by an auxiliary switch m. To open the main switch e, the auxiliary switch m is first opened, causing the motor to start. After a certain travel an adjustable tappet k on the geared member h knocks off the switch lever by impact. A brake n may be brought into action by the movement of the member h so as to stop the motor after a definite time. In the arrangement shown in Fig. 4, the motor remains connected in a shunt circuit after the main switch is opened, and the energy of the motor as it runs down mav be used for reclosing the switch.