GB276603A - Improvements relating to electric rotary converters - Google Patents

Abstract

276,603. Townend, R., Juhlin, G. A., and Metropolitan-Vickers Electrical Co., Ltd. June 21, 1926. Rotary converters; commutating poles and windings.-In a rotary converter subjected to inverted operation, the commutating poles are provided with auxiliary windings so arranged that their excitation per ampere of main current in the machine changes when the action of the machine changes from normal to inverted conversion. Fig. 1 shows a converter in which this is effected by an auxiliary commutating winding 24 which, in normal operation, opposes and with inverted working assists the main commutating winding 15. The converter is shunt-excited at 20 and series-excited by a coil 21 in series with the oommutating coils 24 and energized by an exciter 23. the field coils 26 of which are connected by a change-over switch 27 across a series resistance 16 in the main lead 17 of the converter. When the converter changes to inverted working, the switch 27 is thrown over, by a reverse-power relay or other means, so that the commutating coils 24, 25, which normally oppose, aid each other magnetically, notwithstanding the reversed current in the main leads, and a greater commutating field is produced than that which obtains in normal working. As an alternative to reversing the current in the coil 26 bv a switch 27. this coil may be wound in two opposing parts and switchgear provided so that one part is used for normal and the other for inverted conversion, or so that one which overpowers the other is shortcircuited for normal running and operative for inverted working. In the arrangement shown in Fig. 4, applied to two converters 11, 11<a> in series, with their shunt coils omitted, the normal commutating-pole windings 15 are connected across the continuous-current terminals 17, 19 in series with the series coils 26<c>, 26<d> of the exciter 23 which supplies the series coils 21, 21<a> of the converters. Each converter also has an additional oommutating-pole winding 24, 24a connected across the exciter in parallel with its shunt coil 32 and having a short-circuiting switch 34. The coil 26d, which opposes and is stronger than the coil 26<c>, is short-circuited by a contact 30 during normal operation of the converters and the contact 34 is open. When the converters work inverted, the, contact 30 is opened, for example by a reverse power relay, so that the winding 26<d> prevails and maintains the same exciter polarity, and simultaneously the contact 34 is closed, thereby adding the commutating effect of the coils 24, 24a to that of the coils 15, 15<a>. A resistance 31 or a lead of sufficiently high resistance is connected in series with the coil 26d and diverters mav be used across the coils 26<c>, 26<d> as shown in dotted lines. The auxiliary commutating coils 24, 24a may alternatively be connected in series with the coil 26<d> and the resistance 31 so that they are short-circuited by the contactor 30 during normal operation of the machines and are energized when the operation becomes inverted.