GB815929A - Improvements in or relating to electric control systems - Google Patents

Abstract

815,929. Automatic speed control systems. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Sept. 14, 1956 [Sept. 20, 1955], No. 28138/56. Class 38 (4). In a system for a prime mover driving an alternator, the throttle is electromagnetically controlled through a magnetic amplifier in response to the difference between two direct currents derived from the alternator through a circuit including a rectifier producing a constant voltage and through a further circuit producing a frequency dependent voltage, respectively, and negative feedback to the magnetic amplifier is provided by means responsive to throttle position. Throttle T of the engine E, Fig. 3b, is actuated by a piston P, Fig. 3a, in accordance with current through solenoids 8, 14 in the outputs of self-saturating magnetic amplifiers MA1, MA2, control windings 48-51 of which are energized by the difference in outputs of rectifiers R and RF fed by the generator G. Rectifier RF, which includes in its input a ferro-resonant circuit 41, 42 and a reactor 44 produces across resistor 46 a voltage which is inversely proportional to frequency. Wiper 47 of potentiometer 37 is preset by motor RM to be at the same potential relative to point 39 as point 45 and the amplifier windings 48-51 are thus energized in accordance with frequency error. Bias windings 25, 26, 33, 34 are energized by the output of rectifier R through potentiometers 28 and 31, and feedback windings 59-62 are energized by the potential across the wipers of potentiometers 54, 64, the latter of which is driven by the throttle actuator. A further potentiometer 63 provides for gain adjustment. A voltage proportional to I cos # is developed across lines 65, 74 by potentiometers P1-P6, across the outputs of rectifiers R1-R6, the secondaries S1-S6 of transformers T1-T6 being coupled to primaries 76, 77, 176, 177, 276, 277 which have a large number of turns and are energized by the system phase voltages, and primaries 78, 79, 178, 179, 278, 279 which have few turns and are energized by current transformers 80, 90, 92. The voltage is applied to load compensating windings 70-73 through potentiometers 66 and 67, and load sharing with a second generator is provided by windings LS3, LS5, LS6, LS8 and corresponding windings in the control circuit of the second generator through switch SW and the circuit shown in Fig. 8. Proportioning of the loads is effected by potentiometers 66 and 266. Characteristics and vector diagrams are described with reference to Figs. 5-7 (not shown) and a method of adjusting the frequency sensitive circuit 41, 42 for a different frequency is described with reference to Fig. 4 (not shown). Reference has been directed by the Comptroller to Speciftcation 655,115.