GB624342A - Improvements in or relating to alternating current phase conversion systems - Google Patents

Abstract

624,342. Phase changing. GENERAL ELECTRIC CO., Ltd., HERWALD, N., and STOVE, J. P. July 4, 1947, No. 17695. [Class 38 (ii)] To obtain three-phase currents from a singlephase input, two thermionic amplifiers are arranged to produce single-phase outputs in quadrature which are applied to a transformer arrangement yielding three-phase currents. A single-phase source applied at terminals 5, 4 to a thermionic amplifier 5, gives a single-phase output from a transformer 13 in phase or phase opposition with the input, and applied to a tetrode 16 having an inductance 22 in its output circuit followed by resistance-capacity coupled amplifiers 24 ... 26 gives a 90 degrees phase-displaced output to a transformer 31. The transformers 13, 31 are Scott-connected to give a three-phase output at terminals 46, 47, 48. This may be applied through a transformer 50 to three-phase supply means for ripple control according to the frequency of the source at 3, 4. To compensate the effect of frequency changes on the inductance 22, the source voltage is applied to the grid circuit of a valve 33 having a condenser 38, the potential across which falls with frequency, and the output of the valve 33 after amplification and rectification is applied to a bias resistor 43 in the grid circuit of valve 16, which is of variable mu type.