GB444270A - Improvements relating to the synchronisation of electric machines - Google Patents

Abstract

444,270. Electricity supply. TAYLOR, M. K., and FERRANTI, Ltd., Hollinwood, Lancashire. Oct. 10, 1934, Nos. 28989 and 37239. [Class 38 (iv)] Synchronizing.-Electric machines or systems are synchronized by a grid-controlled discharge tube associated with electric means preventing flow of anode current until voltages derived from the two sources are within predetermined limits, both the anode current and the grid biassing voltage being dependent upon the amplitude, phase and frequency of both systems. A generator with output-terminals 1, 2 is connected to bus-bars of a circuit having terminals 3, 4 by means, not shown, operated when the two are in synchronism, by a switch energized from contactors 42, 43, which are connected by relay 31 when current flows through the valve 18. The valve is associated with the generator and the mains circuit through transformers with primary windings 5, 11, each with three secondary windings. The main anode current is supplied by secondary windings 7, 14 in series, the discharge circuit being completed through contacts 28, 29 when relay 31 is operated. A permanent bias is applied to the grid 17 by secondary windings 9, 15, rectifier 25 and potentiometer 20, through adjustable contact 19 and resistance 23. A negative variable bias is applied to the grid 17 by opposed secondary windings 8, 13 through rectifier 16, condenser 24 and resistance 23. When the two sources of supply are synchronized for a sufficient period, the negative bias thus applied to the grid is reduced to zero and the tube 18 is rendered conducting. Relay 31 is thus operated by winding 44 and contacts 42, 43 are closed to operate the main connecting switch. Contacts 40, 41 are also closed so as to energize hold or coil 39 for relay 31 and pull off coil of relay 30. Contacts 37, 38 being disconnected to cut out the circuit to the cathode heater 36 and contacts 28, 29 break the main discharge circuit through the tube 18. When the generator is switched out, relay 31 is restored to the contacts open position and relay 30 to the contacts closed position, thus rendering the discharge tube ready for operation whenever switch 12 is closed. In a modification, the variable bias is applied to the grid by independent transformers instead of the secondary windings 8, 13, the secondaries of the transformers being so connected that they act in the same direction when the generator and main circuit are in phase. Sharp peak outputs may be obtained by the use in the transformer of cores of such shape and material that they are quickly saturated.