Improvements in and relating to systems of automatic control for synchronous frequency converters

摘要

548,852. Electricity supply. BRITISH THOMSON-HOUSTON CO., Ltd. Dec. 26, 1941, No. 16671. Convention date, Dec. 27, 1940. Drawings to Specification. [Class 38 (iv)] Synchronizing frequency converters.-A frequency converter comprising two coupled synchronous machines is started by connecting one to a polyphase network through voltage reducing means to run up as an induction motor and by energizing the field of the second machine. A frequency responsive relay connected to the second machine causes energization of the field of the first machine at a suitable speed. Relays responsive to the phase relation between the voltages of the second machine and a second network then control a set of four relays which produce successive reversals of the field of the first machine until the voltage of the second lies within a given range of synchronism or opposition with the voltage of the second network, whereupon full voltage is applied to the first machine and in the case of phase opposition a further relay causes reversal of excitation of the second machine. The calibration of the phaseresponsive relays is now changed and they operate upon two of the set of four relays mentioned to cause them to control a reversible motor to move the stator of one of the machines to produce synchronism whereupon the second machine is connected to the second network. The system is controlled by a starting switch and the relays and main switches are electrically interlocked and comprise the requisite time delay elements.