GB640100A - Improvements in or relating to phase multiplying transformers - Google Patents

Abstract

640,100. Transformers. STANDARD TELEPHONES & CABLES, Ltd. Dec. 4, 1947, No. 32034. [Class 38 (ii)] [Also in Group XL (c)] A static phase-multiplying transformer for producing a sine wave polyphase output comprises a first core carrying a polyphase primary winding producing a rotating magnetic flux and a second core carrying a secondary winding having a greater number of phases than the primary, the cores being angularly adjustable to displace the secondary output phases relative to the primary phases. A two-phase primary winding is wound in slots 4, 5 and 6, 7 the secondary winding being wound in slots 8, 9 to 15, 16 giving a normal four-phase winding. By placing two windings in one slot and making certain connections with a 180 degree phaseshift an eight-phase winding may be obtained which can be either star or ring connected. By further doubling the windings per slot two separate secondaries may be had which if connected one in star and the other in ring fashion produce a sixteen-phase output. This result may also be obtained by a single coil per slot, each centre-tapped to provide the starpoint 21 and having two further tappings, e.g. 22, 26, eight phases then being taken from tappings 22-29 and another eight phases from 30-37. The ratio between windings 21, 22 and 21, 17 must be 1: 1.307 in order that all the sixteen-phase voltages may be equal. The relative phase relationships between primary and secondary windings may be varied by angularly adjusting the core 10 relative to core 3 which movement may be effected manually or automatically. Any number of primary and secondary phases may be employed and the rotation may be limited by stops, or unlimited movement may be had by the provision of brushgear. The transformer is particularly useful in multiplex pulse transmission systems to avoid phase distortion due to the time lag between the transmission and reception of signals.