Improvements in or relating to d.c. motor control systems

摘要

1,117,115. Commutator arrangements for dynamo-electric machines; inverting. RACAL COMMUNICATIONS Ltd. 10 Nov., 1965 [10 Nov., 1964], No. 45773/64. Headings H2A and H2F. [Also in Division G1 In a D.C. motor 5 an external commutator circuit 12, including two controlled rectifiers, responsive to the position of the motor shaft is connected between an electric power supply 11 and slip rings 7, 9 so as to supply the armature of the motor 5 with a continuously reversing current. The commutator circuit is controlled by a shaft position indicator 18 which comprises photo-transistors (24, 26, Fig. 2, not shown), blackened screens (42) and a visible or non- visible lamp source (40). The shaft of the motor is divided into non and light reflecting surfaces (32, 34 and 36, 38), the amount of light being reflected controlling the conduction of the photo-transistors. Each photo transistor gives two negative output pulses, (at 54, 56, Fig. 3, not shown), for one revolution of the shaft. These outputs (54, 56) are each transferred by a separate transistor circuit (Fig. 4, not shown), to control the conduction of silicon controlled rectifiers (78, 80, Fig. 5, not shown) of an inverter circuit which provides an A.C. output (at 72), for connection to the slip rings. Speed control.-The speed is adjusted by a variable frequency source 15 which controls the conduction of semi-conductor controlled rectifiers (100, 102, Fig. 6, not shown) forming the speed unit 14 connected to the slip rings. Alternatively these controlled rectifiers (100, 102) may be connected between the supply 11 and the commutator circuit 12, the rectifiers being controlled by pulses from the output of the commutator circuit. As the load on the motor varies so does the phase angle between the outputs of the commutator circuit and the variable frequency source 15 and this controls the conduction of the rectifiers (100, 102) so as to supply current to the armature to maintain the speed constant. A bridge circuit 16 returns energy from the output of the inverter circuit to the supply 11 when the semi-conductor controlled rectifiers (100, 102) are non-conductive. Starting.-The motor may be started by hand, or the S.C.R.'s of the inverter circuit may be connected directly to the slip rings by a switch which temporarily disconnects the inverter output transformer.