GB1010227A - Improved circuit arrangement for synchronous machines - Google Patents

Abstract

1,010,227. Control of A.C. motors. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Nov. 18, 1963 [Nov. 20, 1962], No. 43862/62. Heading H2J. When switch 2 is closed to energize the stator winding 1 of a synchronous motor, current is induced in secondary phase winding A, in the form of unidirectional pulses due to rectifier 5. Pulsating direct current traverses the phase windings B, C, due to rectifier 10, the resultant currentdirection being opposite to that in the winding A. The flow periods are phasedisplaced so producing the equivalent of alternating- current flow along the axis of phase A, the directcurrent component being negligible if the ampere-turns due to the windings B, C are equal in magnitude to those due to the phase A. When the machine reaches synchronous speed, no voltage is induced in the secondary windings, but direct-current is supplied to phase A through transformer 6 and rectifier 5. In another arrangement, the rectifier bridge 5 is connected across a series circuit comprising phase A and parallel-connected phases B, C. The rectifier 10 is connected in series with a resistor across phase A only, Fig. 2 (not shown). The secondary winding may be of the threephase delta type, with one phase supplied through a full-wave rectifier and transformer, another phase shunted by a half-wave rectifier and resistor in series, and the third phase short-circuited by a conductor, Fig. 3 (not shown). In another arrangement the third phase is shunted by a resistor, or two resistors in series, the junction-point therebetween being connected to the full-wave and half-wave rectifiers. In a selsyn system, the primary windings of several machines are connected in parallel, the secondary windings are also arranged in parallel and are connectable as described above for starting, Fig. 6 (not shown). Specification 769,746 is referred to.