Improvements in or relating to rectified power equipment

摘要

696,348. Rectifying; transformers. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Dec. 21, 1951 .[Jan. 26, 1951], No. 29944/51. Class 38 (ii). [Also in Groups XXXVII and XXXIX] The invention relates to a method of reducing the interference with a communication system by harmonics in the A.C. overhead line of a tractions system, the vehicles of which are driven by D.C. motors energized through rectifiers on the vehicle. Each of the motors, which are divided into two groups A 1 , A 2 and A 3 , A 4 is connected to its own pair of rectifiers 41, 42, which may be ignitrons, with which are associated coupled commutating induct. ances. The rectifiers are connected to taps T1-T14 on the secondary winding 35 of the supply transformer, the primary winding 34 of which is supplied through collector 33 from a single phase overhead line 30, harmonics in which may induce interference in a nearby communication system. The actual connections are made through switches A-N, A1-N1, a-n, a1-n1 which are operated by a controller in the sequence shown diagrammatically in the Figure, to vary the tap connections and thereby the speed of the motors. Circulating current suppressor coils P1-P4 are provided. As the controller is operated the rectifiers are so connected to the taps in sequence that each pair has equal and unequal voltages applied to it in turn, and when the voltages applied to the rectifiers of one group of motors are unequal, the voltages applied to the rectifiers of the other group are unequal to the same extent, but the greater voltages are respectively derived from opposite sides of the centre tap. Thus, with the controller in notch 6, switches B, B1, b, b1, C, C1, C, C1 are closed, rectifiers 41, 42 of the motor group A1, A2 are connected through lines L2, L1 to taps T1, T4 unequally spaced from centre tap X, and rectifiers 41, 42 of the motor group A3, A4 are connected through lines L4, L3 to taps T3, T2 which are unequally spaced from the centre tap X by a similar amount but on opposite sides. In this way the arrangements, such as those described in Specifications 682,610 and 682,650 to suppress harmonic interference are unaffected by the unbalance condition of the rectifiers of each pair, while avoiding the need for doubling the number of taps to allow the same number of effective controller steps without producing unbalance.