GB539840A - Improvements in electric motor control systems - Google Patents

Abstract

539,840. Control of D.C. motors. BRITISH THOMSON-HOUSTON CO., Ltd. July 13, 1940, No. 11677. Convention date, July 13, 1939. [Class 38 (iii)] [Also in Group XXXV] Traction or other motors 9, 10 are supplied from the line in series with a buck and boost machine 15 driven by a,line machine 17. The motors are accelerated and decelerated in five stages. Their fields and the field 26 of machine 17 are controlled by an exciter 30. During the first stage, field 33 of the exciter 30 is energized according to the acceleration of a pilot motor 78 driving a flywheel. During The second stage the motor current is prevented from exceeding a limiting value by deriving a voltage from a potentiometer 47 and applying it through a rectifier 45, to the field of a second exciter 41 which supplies through a rectifier 40 a reverse field 32 of the exciter 30. In the third stage the curent of the line machine 17 is prevented from exceeding a limiting value by deriving a voltage from a potentiometer 49 and applying it Through a rectifier 46 to the field of the exciter 41. During the fourth stage the voltage across the motors 10 is prevented from exceeding a limiting value, by deriving a voltage from a potentiometer 50 and applying it through a rectifier 65 to the field 32. In the final stage, the speed of the motors 9 are held at a limiting value by a tuned alternator 51 driven thereby supplying through a rectifier 61 the field of the exciter 41. During deceleration the reverse sequences obtain and give regenerative braking, a relay 69 opening at about 5 m.p.h. so that the pilot motor 78 and flywheel coast to rest. In order to keep the speed of the set 15, 17 constant. a tuned alternator 86 supplies through a rectifier 90 the field of an exciter 82 supplying the field 27 of the machine 15.