GB601175A - Improvements in automatic acceleration control systems for electric traction motors - Google Patents

Abstract

601,175. Control of D.C. motors; electromagnetic switches. RAMSDEN, H. K., and METROPOLITAN-VICKERS ELECTRICAL CO., Ltd.. July 30, 1945, No. 19479. [Classes 38 (iii) and 38 (v)] A control system for a traction motor is provided with a number of sequential accelerating contactors such as Ma-Mc, Fig. 1, operated by a controller and respectively in series with one of operating coils A-C so that energization of coil A opens contacts A1, closes a holding circuit for. itself over contacts A2, and also prepares an operating circuit for coil B by closing contacts A3, a similar operation being effected on contacts B1-B3 and C1-C3 by the operation of contactors Mb and Mc, the preparing circuits being also controlled through the contacts 4 of a currentlimiting relay which is opened by a shunt coil II associated with a holding coil I in the motor circuit, whereby contact 4 is held open and prevents energization of the succeeding contactor until the motor current has fallen to a predetermined value. Energization of coil A also closes line contacts A4, coil B closes contacts B4 to short circuit a resistance R1, and coil C closes contacts C4 to short circuit a resistance R2. Energization of coil C also prepares a circuit for a coil D and a " set-up " coil III, the energization of D acting to close a contact D1 in a diverter circuit R3 for the series field of the motor. The " set-up " coil III is associated with the magnetic circuit of the current limiting relay, and acts in opposition to the winding I, thereby causing the relay armature to fall at a higher value of motor current and compensating for the increased armature current in the high speed position, due to field weakening. The system provides protection should the master controller be moved from the " off " position through several notches rapidly, since the contactors do not operate immediately. Relay construction. The relay contacts 4, Fig. 3, at the ends of terminal members 4a mounted on an insulating bar 5a co-operate with the end contacts of a slidable conducting bridge 4b which is provided with two apertures to receive the parallel limbs of a supporting guide 4d carried by an arm 4e, Fig. 2. A plunger 4c projects from the bridge 4b through a hole in the guide 4d and co-operates with the upper end of an armature 6, the contacts 4b being normally closed on contacts 4 by the pressure of a spring 5b when the armature is inoperative. The actuating coil II of the relay is mounted on a core 11 which carries a shortcircuiting turn 13 beneath the coil for the purpose of providing a delay in the armature release when the circuit including the coil II is broken and allowing time for the holding coil I, mounted on a parallel core 9, to become effective. The coil III which acts in opposition to coil I is mounted on the outer end of the core 9. An adjustable end 10 may be provided to vary the air-gap between the armature and the core 9, and a non-magnetic shim 12 may be interposed between core 11 and the armature.