GB255603A - Improvements in starting arrangements for electric motor converters - Google Patents

Abstract

255,603. General Electric Co., Ltd., and Kahn, M. L. June 9, 1925. Synchronizing dynamo-electric machines. - A. motor-converter having the same pole number in both of the cascaded elements of the machine isstarted as an induction motor, and when it has reached about half the synchronous speed of its alternating-current element its rotor windings are so arranged that single-phase current only can flow such as to bring the machine into synchronism when the continuous-current element is excited. In the form shown, the alternating-current element 1 is connected to the continuous current element 2 in the usual way and the 3- phase coils 13, 14, 15 are connected through sliprings 16, 17, 18 to a two-way switch 25 which on one side 26 connects the coils 13, 14, 15 to the neutral 27 of the 3-wire continuous-current system 6, 7, 27 and on the other side 29 to an ohmic star resistance 32. A switch 34 is included in one of the leads and a short-circuiting device 12 is provided for the rotor coils of the element 1. The set is started as an induction motor by energizing the stator 8 from the supply with the switch 12 open, switch 34 closed and switch 25 set so as to close contacts 29 and open contacts 26. When half synchronous speed is approximately reached, switch 34 is opened and the machine tends to run steadily at half synchronous speed. The fields 9 are then energized by closing the switch 36 and the machine is synchronized, as shown in the voltmeter 35. Thereafter, switch 34 is closed, the inner ends of the coils are short-circuited by the device 12 and switch 25 is thrown over to open the contacts 29 and close the contacts 26 and the set is ready to take up load.