GB243843A - Improvements in or connected with switch mechanism and cable connections for electric motors - Google Patents

Abstract

243,843. Mavor & Coulson, Ltd., and Lawrence, W. Sept. 29, 1924. Switching systems. - Electric switching arrangements for use in controlling motors operating coal cutters &c., in which a trailing cable with plug couplings at each end, connects the motor to the supply are provided with an electrically - operated starting switch or switches at the supply end which can only be closed when the couplings are in position and which is controllable by a switch on the machine. As shown in Fig. 1, electromagnetically operated switch G connects lines 1 - - 3 of the supply cable A to a three phase motor through a trailing cable C having plug connections B, D, at its ends. The circuit of the switch operating coil H is completed across the supply mains through switches E and F and auxiliary lines 4 and 5, the switches being arranged to lock the plug connectors in position when closed, thus ensuring that the plug contacts cannot be exposed when alive. In Fig. 2 the auxiliary switch operating circuit is fed from the secondary of a transformer K the primary of which is connected across the mains by the switch E and the secondary through the switch F and lines 4 and 5. In Fig. 3 the return path for this secondary circuit is through the machine frame and cable armouring. Fig. 4 shows a further modification in which the circuit of the closing coil H of the electromagnetically operated switch is completed across the mains by a relay N the circuit of which is controlled in the manner already described in connection with the coil H of Fig. 3. The switches E<2>, and F<2> in this form not only control the auxiliary circuits at E<1> and F<1> but also carry bridging members of main and reversing switches in the line circuit. The relay N may engage a mechanical interlock P for preventing the switch G from closing otherwise than by the action of the coil H.