GB666723A - Improvements in or relating to field excitation arrangements for electric alternators - Google Patents

Abstract

666,723. Alternators. GENERAL ELECTRIC CO., Ltd., and FRIEDLANDER, E. S. March 22, 1950 [March 23, 1949], No. 7953/49. Class 35. An excitation arrangement for an alternator includes an exciting alternator and a rectifier to feed D.C. to the main alternator excitation and a second rectifier to excite through a Boucherot circuit the exciting alternator from current supplied either by the main alternator or by the exciting alternator itself. The Figure shows a main alternator 10 supplied with D.C. excitation current from an exciting alternator 12 via a rectifier 17, both machines being mounted on the same shaft. The D.C. excitation current for the exciting alternator 12 is fed from the output lines 27, 28 of the main alternator 10 via the transformers 26, 30, 23 and rectifier 21. A condenser 25 is inserted in the circuit of the primary winding 24 of the transformer 23. The capacitance of this condenser and the inductance of the winding 24 are so selected as to provide a Boucherot circuit resonating at the frequency of the main alternator current. In a modification the excitation of the exciting alternator 12 is derived through a Boucherot circuit supplied with A.C. from the exciting alternator itself. In another arrangement, the rectifier supplying excitation current to the main alternator 10 is grid controlled and is controlled by a phase shift network regulated according to the voltage, current and optionally power factor of the main alternator 10. In all the above arrangements the Boucherot circuit may include a saturable reactor or transformer provided with further winding(s) for control purposes.