| 摘要 |
734,589. Automatic voltage/frequency control systems. AMERICAN MACHINE & FOUNDRY CO. May 14, 1952 [May 28, 1951], No. 12205/52. Class 38 (4). The invention relates to automatic voltage and frequency control for electric motoralternator sets, including compensation for surge conditions. As shown, a compound D.C. motor 12 drives a single phase alternator 30, the respective fields 15, 22, being energized from the D.C. supply through carbon-pile regulators 16, 25 such as those described in Specification 733,555. Voltage control (i). Transient control. The alternator output is fed through an autotransformer 60 to a pair of full-wave rectifiers 43, 44 providing outputs of e.g. 150 volts positive and negative with respect to ground. These outputs are applied respectively to a relatively large capacitor C1 and a relatively small capacitor C2 so that the voltage across C2 follows rapid changes, whereas that across C1 does not. The transient voltage fluctuations are transmitted through C3, R4, to the grid of one half of a double triode 50 controlling the alternator field regulator. Voltage control (ii). Steady variations. The output voltage from the rectifiers 43, 44 is applied across a potential divider comprising R2 and a diode 45 with an under-run heater supplied from a secondary 46 on the transformer 60. Changes in the heater voltage vary the internal resistance of the diode, and the resulting change in voltage is applied to the grid of the triode controlling the field regulator. Frequency control. A circuit C10, L10 resonant at a frequency a little above the alternator frequency feeds one half of a double diode 65 to a capacitor C15. The other half of the diode is supplied through a potentiometer P2 fed from the alternator and phaseshift network R12, C12. Since C10, L10 provides a phase shift of about 140 degrees leading, R12, C12 are arranged to produce a shift of about 40 degrees lagging so that the two voltages are 180 degrees out of phase and pulses of opposite polarity are applied simultaneously to C15, and there is no resultant charge at the required frequency. The voltage across capacitro C15 is applied to the other half of double triode 50 to control the motor field regulator 16. To provide prompt correction for transient changes in the D.C. supply voltage the positive bus-bar is connected to the grid of the speed control triode 50 through C18, R18. |
