GB232968A - Improvements in and relating to alternating current dynamo electric machines - Google Patents

Abstract

232,968. British Thomson-Houston Co., Ltd., (Assignees of Hull, J. I.). April 23, 1924, [Convention date]. Alternating-current motors; exciting.-A self - excited synchronous motor starting up as an induction motor and running into synchronism without external devices comprises a polyphase winding 2 fed through slip-rings 5, a commutator winding 1 connected to a polyphase winding 7 and resistances 8 permanently connected across the phases of the winding 7. A permanently connected reactance 9 prevents excessive current at starting from flowing into the commutator winding, which, as the motor runs into synchronism supplies continuous current excitation to the winding 7. The resistances 8 are of such a value that they do not produce excessive slip on heavy loads but allow maximum starting- torque and take little energy when synchronous speed is reached. In the arrangement according to Fig. 2, the stator has separate phase windings 10, 11 in quadrature, each with a permanently connected resistance 8 and functioning as a twophase short-circuited secondary at starting, continuous current excitation being produced in one phase under synchronous conditions. According to the arrangement in Fig. 3, the independent permanently short-circuited stator windings 13 are employed for starting and a separate exciting winding 15 is provided, the windings 13 functioning as dampers during running conditions. The windings 13, 15 are located in slots as shown in Fig. 4, the reactance 9 being dispensed with. Specification 210,936 is referred to.