GB625740A - Improvements in and relating to control systems for direct current motors - Google Patents

Abstract

625,740. Exciting dynamos. BRITISH THOMSON-HOUSTON CO., Ltd., and MAGGS, A. H. July 25, 1946, No. 22189. [Class 35] [Also in Group XXXVII] A multi-polar shunt or compound wound direct-current constant-speed generator has a wave-wound armature 1, and the shunt field winding is divided into two sections, one section, 3a, being wound on a certain number of poles only, and the other section on the remainder of the poles. A series motor 4 is provided with field windings 5 and 6, adapted for forward and reverse operation respectively. Forward and reverse solenoid-operated switches, 9 and 11, are interposed between the motor and generator, the operating-coils, 10 and 12, of these switches being adapted to carry the generator shunt field current. One of the main switches, 9 or 11, is closed by the operation of four control switches, comprising the movable arms 13 and 16, and the contacts 14, 15 and 17, 18, respectively, according to whether forward or reverse, high or low speed operation is required, the closing of the generator shunt field circuit by one of the control switches causing the generator to self-excite at a high or low voltage according to whether the whole or a part of the generator field winding is in circuit. The control switches are shunted by resistors 19-22 having such values that the generator is de-excited at a rate, when a control switch is opened, such as to prevent a sudden interruption of the field current and to ensure that the main switch is not opened until the motor current has dropped to a value at which burning of the contacts is avoided. A brake coil 7 may be provided. The motor may adjust a variable-pitch propeller. Specification 587,657, [Group XXXVII], is referred to.