GB895113A - Improvements in and relating to electric closed-loop control system - Google Patents

Abstract

895,113. Control of motors. ENGLISH ELECTRIC CO. Ltd. March 23, 1959 [March 21, 1958], No. 9229/58. Class 38 (3). [Also in Group XXXV] In a motor control system, a primary reference signal, selected by a control-member, is amplified to form a secondary reference signal and the rate of change of the secondary signal is limited by feed-back responsive to said rate of change varying the energization of the amplifier. As shown, a control lever 17 moves a slider 16a of a potentiometer 16 to derive a primary reference signal, representative of the desired direction and speed of rotation of a motor, not shown, which is fed to an input winding 13a of a magnetic amplifier 13. A secondary reference signal from the amplifier is opposed by the output of a tachogenerator 12 coupled to the motor and the resultant control signal through change-over contacts 15a, 15b is fed to a negative error suppressing device 11. Positive-going signals are fed to a control winding 10a of a torque controller 10 for the motor. A change-over device 14, actuated in dependence on the sense of the control signal, conditions the motor for driving or braking mode of operation. The changeover contacts 15a, 15b are actuated by a device, not shown, responsive to whether the motor is motoring or braking. The secondary reference signal is fed through a differentiating circuit 19a, 19b to a feed-back amplifier 18. The output of the amplifier 18 energizes a control winding 13b, through a rectifier 22 or 23, when the rate of change of signal exceeds a predetermined positive or negative value set by a slider of a potentiometer 20. A separately-excited D.C. motor is controlled by having the armature supplied through a grid-controlled current converter, the grid-phase of which is varied by the torque controller as disclosed in Specification 892,231. A wound rotor A.C. induction motor is controlled by varying the rotor resistance by the torque controller and during braking operation connecting the stator to a D.C. supply or low-frequency A.C. supply. The system may be modified by leaving out the biasing arrangement for the control winding 13b.