GB562741A - Improvements in and relating to frequency changer set - Google Patents

Abstract

562,741. Frequency changing. BRITISH THOMSON-HOUSTON CO., Ltd. March 31, 1943, No. 5147. Convention date, April 1, 1942. [Classes 38 (ii) and 38 (iv)] A frequency changer comprises a wound secondary induction machine 12 mechanically coupled to a synchronous machine 13 connected to a network 11 operating at one frequency, one winding of the induction machine being connected to a network 10 energized, or to be energized, at a different frequency. The other winding of the machine 12 is connected to an auxiliary synchronous machine 16 operating at a frequency corresponding to the difference between the synchronous speed of machine 12 and the speed, above or below synchronism, at which it actually runs. The main and auxiliary synchronous machines 13, 16 are coupled respectively to D.C. machines 15, 17, the armatures of which are connected in series. Excitation for the synchronous and D.C. machines is provided by an exciter 21, and in each case is controlled by a rheostat 22, 23, 26, 27. By control of the excitation of the D.C. machines, the extent and direction of power flow through the set may be regulated, and regulation of power factor may be effected by control of the excitation of the synchronous machines. Either or both of these controls may be effected automatically by coupling the corresponding rheostats to reversible servomotors controlled respectively by contactmaking watt-meters or power factor meters. An induction motor 28 may be provided for use in starting.