Device for the pulse control of a between a direct current source and a dc motor and a main thyristor arranged quenching thyristor associated therewith.

摘要

1,255,933. Control of D.C. motors. LANSING BAGNALL Ltd. 23 June, 1969 [1 July, 1968], No. 31386/68. Heading H2J. [Also in Division G3] A series motor 4 is supplied from battery 1 through thyristor 7 having a commutating arrangement comprising capacitor 22 coupled between rectifiers 7,21, which are triggered alternately, the charge on the capacitor being increased by the action of transformer 25. Triggering signals for the rectifiers 7, 21, are derived from an astable multivibrator, the passage of triggering pulses for the thyristor 7 being prevented when a reactor is saturated by coil 6 in series with the motor. The level of armature current to produce saturation is varied by adjusting the position of a permanent magnet. The trigger network for the rectifier 21 comprises a control transistor which is coupled to the trigger network for the rectifier 7. When the latter conducts, the control transistor also conducts, the next succeeding pulse to the thyristor 21 being prevented whereby the period of conduction of the thyristor 7 is maintained provided that the armature current remains below a predetermined level. Coils 13, 14, of reversing contactors 9, 10, are in parallel with the thyristor 7, so that, if the conduction period of the thyristor is prolonged, the current through the coils decays and the voltage across resistor 17 decreases. A signal is then developed to prevent the passage of triggering pulses to the thyristor 7.