| 摘要 |
883,162. Alternators; automatic voltage control systems. SIEGLER CORPORATION. June 8, 1960 [June 12, 1959], No. 20111/60. Classes 35 and 38 (4). An exciter system for an alternator is regulated to prevent excessive excitation in the event of a fault. Generator 10 has a field winding 11 excited by an exciter system comprising a current portion 18 supplying most of the excitation, and a voltage section 19 sufficient to provide no-load excitation and on-load regulation under normal conditions. Voltage section 19 includes zener diodes 29, 30 in the emitter-base circuit of a transistor 31 so that when the voltage across resistor 26, which depends on the output voltage of the alternator, exceeds a certain value the zener diodes conduct, causing transistor 31 to conduct so that current flows in the control windings of magnetic amplifiers 34, reducing the current in the output windings, and hence the excitation current flowing in conductor 37. Current section 18 comprises current transformers 40 connected through rectifier 43 to conductor 37, and the secondary winding of each current transformeris shunted by back-to-back pairs of silicon controlled rectifiers 45, 46, having resistors 51 in series. The control electrodes of rectifiers 45, 46 are connected to individual secondary windings of a pulse transformer 62. A D.C. transformer 64 has a primary winding in conductor 37 and a secondary winding 65 energized with A.C. from a permanent magnet generator or other source. If the current in conductor 37 exceeds a predetermined value, the impedance of secondary winding 65 becomes sufficiently low so that the voltage across a resistor 68 exceeds the breakdown voltage of a zener diode 72, causing current to flow in the primary winding of pulse transformer 62. This renders rectifiers 45, 46 conducting, shunting current transformers 40 so that the excitation current supplied to field winding 11 is reduced. |
