Improvements in induction motor systems

摘要

1,034,443. Control of A.C. motors. BAILEY METERS & CONTROLS Ltd. Sept. 7, 1962 [Sept. 8, 1961], No. 32267/61. Heading H2J. One of the stator windings of an induction motor is duplicated by an opposed winding, these windings being selectively energizable through respective poles of a double-pole semi-conductor switch, which is also operable to disconnect the two windings from the supply. In another arrangement, a stator winding is connected to the centre secondary tap of a supply transformer, which may be an auto transformer, and is also connected selectively to either end of the secondary winding. A threephase motor has delta-wound stator windings which are connected through the switch to a supply transformer having a double-delta wound secondary winding. Alternatively, the stator windings may be double-delta wound, the sets of windings being arranged in reverse phase sequence and having a common winding. The pairs of ends of the windings remote from the common winding are connected to respective poles of the two-pole switch. This switch may comprise four silicon-controlled rectifiers, arranged in pairs, each pair defining a pole of the switch and the rectifiers of each pair being arranged in parallel opposition. As shown, each controlled rectifier 40 is protected against reverse current by diode 41 and is fed with triggering pulses from transistor pulse generator 44 coupled to protective circuit 46. Zener diode 52 limits positive excursions of the trigger pulse, diodes 50, 52, prevent negative pulses being applied to control electrode 51, and the elements 54, 53, 52 are arranged to limit the trigger voltage at terminal 51 to zero when the anode of the controlled rectifier is negative. The generator 44 may provide pulses in response to an error voltage indicating the displacement of a motor-driven element from a set position. When the rectifier 40 conducts, the generator 44 ceases to supply pulses.