GB1435316A - Dc motor control system - Google Patents

Abstract

1435316 DC motor control BROWN BOVERI & CIE AG 24 April 1973 [25 April 1972] 19215/73 Heading H2J A D.C. motor control system comprises two D.C. chopper regulators including a series circuit comprising two thyristors T 1 T 2 (Fig. 1) each with an antiparallel reverse current diode D 1 D 2 , connected across a D.C. source 1, 2. A D.C. motor 3 in series with an inductance L 1 is connected across T 2 and a common quenching circuit is provided by a series resonance circuit comprising a capacitor C 1 and an inductor L 2 . The resonance circuit oscillates through T 1 which is quenched upon completion of half a period of oscillation. C 1 is then changed in the opposite direction through diode D 2 . The speed of the motor is controlled by variation in the mark/space ratio of the pulses provided by thyristor T 1 . and when regenerative braking takes place T 2 controls the armature current and during the "OFF" periods of T 2 the charge on C 1 flows through diode D 1 back to the supply. L 2 , C 1 also function to quench T 2 . In a modification Fig. 2 (not shown) components L 3 L 4 , D 3 D 4 and T 3 T 4 are added to charge capacitor C 1 from the supply instead of from the regenerative voltage of the motor during braking, whereby to give consistent quenching of T 2 by the charge in C 1 , otherwise if the motor is rotating too slowly the voltage generated and hence the charge in C 1 will be too low for this purpose. In another embodiment Fig. 3 (not shown) the L 2 C 1 resonance circuit is shunted by an anti-parallel pair of thyristors (T 5 T 6 ) or a triac, in series with a further inductor (L 3 ). Alternatively each chopper may comprise a triac or a pair of antiparallel SCRs.