Patent GB-474430-A (GB)
Title: Improvements in or relating to electric motor control systems
IPC: B60L15/04
Filed: 1936-04-30
Abstract: 474,430. Master control of D.C. motors; actuating controllers. GENERAL ELECTRIC CO., Ltd., and CROFT, E. H. April 30, 1936, No. 12353. [Class 38 (iii)] A remote control system for motors resistance controlled when connected in each of a number of different circuit connections, comprises a group of switches arranged to control a resistance step-by-step for each motor circuit connection, and provided. with an operating part always moved in the same direction by power means, and switching means for effecting the different motor circuit connections provided with an operating part normally at rest during operation of the group of switches, a mechanical connection between the two operating parts becoming effective at the appropriate stages to effect operation of the switching means by the operating part of the group of switches. The invention is described for a system in which the group of switches remove resistances 9, 10 from circuit, in steps, during three stages of control during which the motors 1, 2 are connected in series, then in parallel, and finally with their fields 3, 4 shunted by the resistances, and in which a servomotor operating the switches is under the control of a master controller having corresponding controlling positions. Upon operation of the master controller to its full " on position, line switches LS1, LS2 close to connect the motors to the supply in series, and the servomotor operates a resistance cam-shaft controller mounted on a shaft 30, to close contactors 18-27 and 28-37 in turn and remove the resistances 9, 10 in steps. When the cam-shaft 30 has rotated 340‹ and closed the contactors 27, 37, a projection 33 on a disc 31 fixed to the shaft 30 engages a roller 41 carried by a disc 36 secured to a cam-shaft 35 of the combination switches S1, P1, P2, P3, P4, WF1, WF2. Thus, the combination group of switches is moved to its full series position, a switch S being closed so that the full series circuit is maintained when the resistance controller shaft 30 moves forward to open all its contactors. When the shaft 30 starts on its second revolution, after 10‹ rotation, a projection 34 on a second disc 32 on the shaft 30 engages a roller 42 on the disc 36 and moves the combination switch shaft 35 to its first parallel position. When the resistances 9, 10 have again been removed by rotation of the shaft 30, the projection 33 engages a further roller 43 to rotate the shaft 35 to effect the full parallel connections. After further rotation of the shaft 30 the projection 34 engages a roller 44 to rotate the shaft 35 into a position where the weak field connections are made. In a modification, Fig. 3 (not shown), the shaft 35 is provided with two discs having shoulders engaged by respective claws actuated by springs. These claws are moved against their springs by means of a pair of cam discs mounted on the shaft 30, the cams having radial faces whereby the strained springs are released to operate the shaft 35 through the pawls. In a simpler arrangement, Fig. 4 (not shown), the shaft 30 has a single cam disc with a radial face which operates to engage a spring-biassed pawl with a ratchet wheel on the shaft 35, against a spring which when released effects movement of the shaft 35. The shaft 35 is provided with an auxiliary power device for returning it to its normal position when the master controller is returned to its " off " position. The resistance cam switches are such that a contactor will not open until a succeeding one has closed.