GB479056A - Improvements in electric motor control systems, particularly for ship propulsion - Google Patents

Abstract

479,056. Control of D.C. motors. BRITISH THOMSON-HOUSTON CO., Ltd., JEWITT, D. E., and MARSH, R. D. July 30, 1936, No. 21159. [Class 38 (iii)] In a control system for a D.C. motor 1 supplied from a constant voltage source 10 with speed variation by field control, particularly for ship propulsion, a booster generator 2 driven by or independently of -the motor has its armature connected to control the current in the field winding 7 of the motor, the booster having differential exciting windings 8, 9, the former of which is connected in-series with the armature winding of the motor and tends to cause the polarity of the booster to be such as to strengthen the motor field, while the latter is connected to the supply and tends to decrease the strength of the motor field. In the arrangement shown in Fig. 1 (Prov.), the constant voltage source is constituted by four similar generator sets adapted to be connected in parallel to the motor, and the windings 7, 9 are energized through rheostats 5 having four positions I ... IV corresponding to the number of generators in use. The motor is started up through a controller 3, which closes the circuit of the winding 9 at 11 after all the starting resistance has been cut out. The speed of the motor is controlled by a shunt field regulator 4, which is interlocked with the controller 3 to ensure that the latter can only be operated when the regulator 4 is in the " resistance out " position. The two field windings 8, 9 of the booster 2 neutralize each other when the supply current is at its correct value corresponding to the setting of the rheostats 5 ; if the current increases beyond this value, the booster increases the field strength of the motor 1. In the modified arrangement shown in Fig. 1 (Comp.), the field winding 7 of the motor is connected in series with the armature 2 of the booster directly to the supply 10, and speed control is effected by a rheostat 4a in series with the shunt field 9 of the booster. The rheostat 5, with four positions I ... IV corresponding to the number of generators in use, is also connected in the latter circuit. If desired a third winding may be provided on the booster and supplied from the booster terminals.