GB386716A - Improvements in electric motor control systems - Google Patents

Abstract

386,716. Master control of D.C. motors. WHYMAN, F., Arncott, Greenway Road, Timperley, Cheshire, and ASSOCIATED ELECTRICAL INDUSTRIES, Ltd., Crown House, Aldwych, London. Sept. 17, 1931, No. 26084. [Class 38 (iii).] Regenerative braking.-A pair of traction motors A1, A2 are connected as series wound motors during motoring by an electromagnetic switch 8, and during regeneration this switch is thrown over so as to connect the motor armatures to return current to batteries 3, 3a, the fields being separately excited by an exciter E, whose field resistance FR is shortcircuited under automatic control so that a substantially constant regenerated current is obtained as the motors slow down, the automatic control being effected by the same current limit relay 7 as is used to effect automatic acceleration during motoring. The control system, Fig.- 3 (not shown), includes a master-controller having start, series, and parallel motoring positions on one side of its off position, and a single regenerative position on the other side. In the motoring positions contactors are closed sequentially under control of the current limit relay 7 to exclude starting resistances 4<1>, 4<2>, rearrange the motors in parallel and again exclude the resistance. Movement of the master controller to the regenerative position causes all contactors to open as it passes through the " off " position. When the regenerative position is reached, the ollowing sequence of operations occur. An auxiliary relay is energized only when the contactors 10 and G have opened. When this relay is energized, its contacts complete the circuit for the coil that moves the switch 8 to the generating position. Auxiliary contacts on the switch 8 then complete a circuit to the coil of the exciter contactor E1, which when closed completes a circuit, provided that the contactor for the auxiliary motor driving the exciter is closed, to the coils of the contactors 10, and LS1. Thereafter contactor operation progresses to the full series position, after which auxiliary contacts on the switch 8 deviate the control by the current limit relay 7 to the actuation of the contactors for short-circuiting the exciter field resistance FR. When motoring is resumed, the switch 8 is moved to the motoring position but only after the auxiliary relay is again energized. Thus movement of the switch 8 can only be made when contactors 10 and G are open.