GB1380147A - Control systems for electrical motors - Google Patents

Abstract

1380147 Control of several DC motors MOSKOVSKY ORDENA LENINA I ORDENA TRUDOVOGO KRASNOGO ZNAMENI INSTITUT INZHENEROV ZHELEZNODOROZHNOGO TRANSPORTA and TALLINSKY ELEKTROTEKHNICHESKY ZAVOD IMENI MI TALLIN-1 KALININA USSR 9 May 1972 21558/72 Heading H2J A control system for the D.C. driving motors of an electric train comprises a step-down transformer 1 whose primary winding 2 is energized via a current collector 4 and whose secondary winding consists of sections 7 ... 10 respectively controlled by contactors 12, 13, 14 and thyristors 15, 16 to supply a rectifier 11 which feeds two groups 18, 19 of series traction motors, the groups being interconnected by resistors 30, 31 and a contactor 32 and each group being controlled by a respective contactor 24, 29. When operating in the driving mode, contactors 24, 29 are closed and contactor 32 is open so that the armatures 20, 21, 25, 26 and field windings 22, 23, 27, 28 receive the output voltage of the rectifier 11, which voltage is varied from zero to a maximum value by successive closure of the contactors 12, 13, 14 and variation of the firing angle of the thyristors 15, 16. After the maximum voltage has been reached, further speed increase may be obtained by decreasing the value of resistors 30, 31 to vary the current through the field windings 22, 23, 27, 28. When braking is required, the contactors 12, 13, 14, 24 and 29 are opened, the thyristors 15, 16 are made non-conductive, the contactor 32 is closed and the firing angle of the thyristors 15, 16 is then gradually increased. The motors then operate as separately-excited generators, whose armatures are loaded by the resistors 30, 31 and whose field windings are controlled by the thyristors 15, 16, control of which provides regulation of the braking force. Such a control system may be conventional and provide stabilization of the braking characteristics. Alternatively, this stabilization can be achieved by inserting, in each motor group and between the members 21, 22 and 25, 28, a stabilizing rheostat (33, 34) shunted by a contactor (35, 36), Fig. 2 (not shown), the contactors (35, 36) being opened during the braking condition so that the rheostats (33, 34) carry both the field and armature current, variation of the latter producing an automatic compensating variation of the field current. Normally, the contactors (35, 36) are closed during driving, but may be left open for a certain time during starting to allow the rheostats (33, 34) to be adjusted to decrease the initial current surge and the resultant jerk of the train. Members 1, 11 may be replaced by an equivalent circuit using solid state controlled rectifier devices.