GB276467A - Improvements relating to electric rotary converters - Google Patents

Abstract

276,467. Townend, R., Juhlin, G. A., and Metropolitan-Vickers Electrical Co., Ltd. June 21, 1926. Rotary converters; commutating poles and windings.-The series field winding of a rotary converter is fed from a separate exciter, of which the field magnet is excited by a current proportional to the main current of the converter, but of which the sense remains constant when the sense of the main current changes. Auxiliary interpole windings may be provided by means of which the interpole excitation per ampere of line current may be changed when the converter changes from normal to inverted operation. The converter 11, Fig. 1, is provided with a shunt field winding 20, an interpole winding 15, and a winding 21 supplied from an exciter 23. The field 26 of the exciter is connected across a resistance 16 in the main continuous-current circuit through a reversing switch 27 which may be operated by a reverse current relay. An auxiliary interpole winding 24 in series with the winding 21 acts in opposition to the interpole field in normal operation, but during inverted operation, the current in the winding 15 is reversed, so that the windings 15, 24 assist each other. If a different degree of compounding is required during inverted operation, one contact of the reversing switch may be connected to the resistance 16, as shown by the dotted line, instead of to another contact of the switch. In a modification, the exciter field winding is in two portions wound in series opposition, and one or both portions may be provided with short-circuiting switches actuated when the operation of the converter is reversed. In another modification. Fig. 4, shown as applied to two converters 11, 11<a> connected in series on the continuous-current side, the exciter 23 has a shunt field winding 32 and two opposing windings 26<c>, 26<d> in series with a resistance 31 in the main circuit. The main pole winding 21, 21a of the converters are connected in parallel- .across the exciter brushes. Shunt windings are omitted as the exciter is given a compound characteristic. The auxiliary interpole windings 24, 24a are connected in series with one another and with a contactor 34 across the exciter brushes. In normal operation, the winding 26d is shortcircuited by a contactor 30 and the contactor 34 is open. For inverted operation, contactor 34 is closed so that the interpole windings 24, 24a assist the main interpole windings 15, 15a, and contactor 30 is opened whereby the exciter field winding 26d comes into operation and overpowers the effect of the winding 26<c>. In a modification, the auxiliary interpole windings are connected in series with the winding 26d and resistance 31 so as normally to be short-circuited by the contactor 30.