| 摘要 |
1,096,056. Exciting polyphase machines; control of A.C. motors. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Sept. 2, 1964 [Sept. 4, 1963; Jan 27, 1964], No. 34990/63 and 3412/64. Headings H2A and H2S. In a system for controlling the undirectional excitation current of a polyphase A.C. machine e.g. a generator or a synchronous induction or synchronous motor 1, an exciting winding 5 of the machine is connected to receive unidirectional exciting current from a full-wave rectifier bridge 6 connectible to an A.C. source 7 and having a controlled rectifier 15 as the rectifying element in at least one arm thereof, and a control circuit means 14 is operable when the machine load current exceeds and/or when the line voltage is less than respective predetermined values to determine the proportion of each half cycle that the controlled rectifier is conductive such proposition being in dependence on the magnitude of the current excess and/or voltage drop. The latter are detected by current and voltage transformers 36 . . . 38 which causes a rectifier 40 to render conductive, in turn, transistors 16, 17 and the rectifier 15. In Figs. 2 and 3, controlled rectifiers 15 are provided in two arms of the bridge 6 in which case the control circuit is duplicated and a constant minimum voltage bias is applied to one of them. The excitation may be conveyed to the rotor 4 in a brushless, or otherwise, manner, and may be polyphase. |
