GB518549A - Improvements in or relating to voltage regulating systems for alternating current generators - Google Patents

Abstract

518,549. Automatic control systems. DAHLGREN, F., and ALLMANNA SVENSKA ELEKTRISKA AKTIEBOLAGET. Aug. 26, 1938, No. 25150. [Class 38 (iv)] Voltage.-The voltage of an alternator is automatically regulated by a saturable choking coil in series with one of three windings on an exciter, this choking coil being variably saturated in accordance wth the alternator voltage. The saturation-is further controlled to prevent hunting in accordance with changes in the exciter voltage and a frequency-responsive correction may 'also be applied. The sub-exciter field has a shunt winding 11 and two mutually opposed windings, one 22 being fed with constant current and the other 21 fed through the inductance 15 and a rectifier 16. In one arrangement, Fig. 1, the winding 21 is excited from the alternator voltage 2 and in a modification a constant voltage A.C. supply is used. In the first case the choking coil is variably self saturated by the regulated voltage and in the second a separate saturating winding is fed from the alternator voltage through a rectifier. The adjustable anti-hunting provision is a saturating winding 24, fed from the exciter terminals through' a resistance and a transformer 25 or other device producing current variations in proportion to the rate of change of exciter volts. An auxiliary saturating winding 23 may be supplied from the alternator through a tuned circuit 20 so as to eliminate the influence of frequency variations. In the modification the constant D.C. for the winding 22 and the constant A.C. voltage for the winding 21 are obtained from a double current generator on the sub-exciter shaft.