GB621375A - Improvements in and relating to phase converters - Google Patents

Abstract

621,375. Phase changing. BRITISH THOMSON-HOUSTON CO., Ltd. (General Electric Co.). Jan. 19, 1945, No. 1604. [Class 38 (ii)] In a phase converter interconnecting single and polyphase circuits, a transformer has n sets of inductively coupled windings, n windings, one from each set being connected in series across a single-phase circuit and n other windings, one from each set being connected symetrically to the polyphase circuit, the turns ratios being so arranged, and reactances being so connected to the polyphase windings that the polyphase load is balanced for a given load on the single-phase circuit. Three-phase, similar, input, transformer windings 1, 2, 3 are meshconnected, and the corresponding output windings 11, 21, 3<SP>1</SP> of which 3<SP>1</SP> has only half the turns of equal windings 1<SP>1</SP>, 2<SP>1</SP>, are connected in series with 3<SP>1</SP> reversed to a single-phase circuit 4. To equalize the currents of inputs phases 1, 2 with the current in phase 3, and to bring them into phase with their respective line voltages, assuming unity P.F. of the single-phase load, capacitor 7 and inductance 6 are connected across phases 1, 2, respectively. The winding 1 may be wound as an auto-transformer to supply a higher voltage to capacitor 7, Fig. 3 (not shown), while to provide inductance in phase 2 this may be wound on a core having an air-gap. A suitable three-phase core is described, Fig. 4 (not shown), of F-shaped stampings placed opposite each other, with a variable air-gap between the two projections forming the middle leg. With variation in load the values of capacitor 7 and inductance 6 must be suitably altered to maintain the supply in balance, while with variation in power factor, the turns ratio must be altered in addition. The transformer works equally well supplying a three-phase load from a single-phase supply.