Speed regulating systems for a.c. motors

摘要

727,076. Automatic speed control systems. BRITISH THOMSON-HOUSTON CO., Ltd. Nov. 16, 1953 [Nov. 25, 1952], No. 29801/52. Class 38 (4). [Also in Group XXXVII] The speed of a single-phase A.C. motor is controlled, in accordance with the difference between a speed responsive and a reference voltage, by a pair of reversely connected thyratrons (or the like) in series with the motor. As shown, reversely connected thyratrons V2, V3 are connected in series with a repulsion motor M and the firing angle is controlled by a saturable reactor SRA having its saturating winding SRD in the anode circuit of a pentode V1 controlled in accordance with the difference between a reference voltage from potentiometer P1 and the voltage of a tachometer generator TG driven by the motor. The grid circuits of the thyratrons are coupled by a transformer T2P to provide the required 180 degrees phase shift in the firing voltage. Starting arrangements.-The starting relay CR is energized through thermal delay switch TDS, to allow the thyratrons to heat up. An auxiliary contact cr4 closes the supply to the valve V1 whereby the reference voltage builds up in a time dependent on C2 to provide gradual acceleration. Modifications.-A larger motor may be controlled by ignitrons " anode fired" by the thyratrons V1, V2, Fig. 2 (not shown).