| 摘要 |
938,302. Supply systems for railway vehicle services. J. STONE & CO. (DEPTFORD) Ltd. May 9, 1962 [July 18, 1961], No. 26047/61. Class 38 (4). An electrical supply system comprising a variable-speed alternator has the excitation of the alternator so arranged that the current delivered by the alternator remains substantially constant over a wide range of speed. The alternator 3 is provided with main and auxiliary field windings 4, 5 wound in an additive sense, the main winding 4 being excited in accordance with the load 1 on the alternator, the auxiliary winding 5 being excited in inverse proportion to the output frequency of the alternator by way of a frequency-sensitive circuit 6, the choke 9 of which saturates at high frequencies. The excitation of the auxiliary winding 5 is thus greater at low frequencies so that the full output of the alternator 3 is developed at very low speeds. The alternator is preferably a high-frequency unsaturated machine. The system may incorporate a variable resistor whereby the output level of the alternator may be adjusted. |
