GB1440949A - Controlling commutating means for groups of generating elements of an electrochemical generator supplying current to an electric motor - Google Patents

Abstract

1440949 Control of DC motors SOC ANON AUTOMOBILES CITROEN 18 Sept 1973 [21 Sept 1972] 43852/73 Heading H2J A control system for a DC motor comprises at least two groups of generating elements of an electro-chemical generator supplying the motor, commutating means to connect the groups in series or parallel according to the power required by the motor, a chopper supplying the motor with pulses of current also in dependence on the power required and control means to actuate the commutating means in synchronism with the operation of the chopper. The invention is particularly applicable to the motor control system described in Specification 1,440,790 and Fig. 1 shows a circuit arrangement whose generating elements 1, 2 are controlled by electro-mechanical contactors 5a, 7a 8a, 5b, 7b, 8b in the manner described in that Application, the use of the series motor 3 to drive a vehicle causing frequent operation of the contactors under the control of members 6, 16 which, with the chopper 4, are also described in the aforementioned Application. To ensure synchronism of chopper operation with contactor actuation, the circuit additionally includes a member 14, AND gates 15, 17, flip-flop 18 and a member 19, which delivers a signal when contactors 5a, 5b are closed to one of their fixed studs 7a....8b. Member 14 receives input signals 14a, 14b, 14c respectively representative of the average motor voltage, the average motor current and the control signal to the chopper 4 to produce a desired power or torque. Output signals 14d, 14e respectively correspond to series or parallel connection of the groups 1, 2, the signal 14d also applying a signal 4a to the chopper to make it non-conductive, which condition produces an output signal 4b. A signal 4c prevents conduction of the chopper. If a signal 14d is produced to change groups 1, 2 from parallel to series connection, the chopper 4 is turned off (since it will be continuously conductive under parallel connection, as described in the aforementioned copending application) and produces signal 4b to enable gate 15, whose output 16a causes the flip-flop 16 to actuate the contactors. Flip-flop 16 also produces a signal 16d to change flip-flop 18 and so produce signal 4c to maintain the chopper non-conductive. When the contactors have changed over, the member 19 changes the flip-flop 18 to remove signal 4c and so allow the chopper to resume normal operation. When a signal 14e is produced, the chopper will be periodically non-conductive for the existing series connection of groups 1, 2 and hence, upon production of the signal 4b, gate 17 is enabled to change flip-flop 16 and so cause operation of the contactors and members 18, 19 as previously described. In a modification (not shown), the member 14 has only one output and the arrangement is such that the presence or absence of a signal at this output corresponds to one or other of the connections of groups 1, 2. Fig. 1 may be modified by replacing the two contactors with a single on/off switch (20) connected between opposite polarity terminals of the groups 1, 2 and with diodes (21a, 21b) connected between like polarity terminals, Fig. 2 (not shown). Fig. 3 shows an arrangement similar to the latter modification, but with the on/off switch replaced by a thyristor 22 controlled by trigger circuit 22b, AND gate 23 and members 4, 14, a signal 14d being produced when series connection is required and causing firing of the thyristor 22 each time conduction of the chopper 4 produces an output signal 23b.