GB1045573A - Improvements relating to the excitation and control of dynamo-electric generators - Google Patents

Abstract

1,045,573. Automatic voltage control. SELECTRA Ltd. and E. W. KREBS. Feb. 15, 1963 [Nov. 22, 1961], No. 41854/61. Heading G3R. The excitation circuit of an alternator is associated with a known current and voltage compounding arrangement which is modified by the provision of a transductor connected as a variable impedance acting as a by-pass circuit for the excitation current. As shown, current and voltage components of compounding are derived from a current transformer 15 and a linear reactor 17 respectively and are applied over a rectifier 12 to the field winding 11 of an alternator 10, giving a "coarse" regulation to constant output voltage. A self saturating transductor 20 with two operating windings 21 and oppositely poled rectifiers 23 connected as a bridge circuit has the A.C. corners 24, 25 of the bridge connected to the A.C. input of rectifier 12 and the D.C. corners 27, 28 of the bridge connected to a resistor 26 to which is applied a control voltage which is dependent upon the output voltage of the alternator and which is derived over a transformer 29, a variable resistor 31, and a rectifier 32. The arrangement is such that the impedance of the transductor 20 is controlled in dependence upon output voltage variations, whereby the excitation current by-passed through the transductor is varied in a corrective manner to give a "fine" voltage regulation. Three-phase embodiments are described with reference to Figs. 2, 3 and 4 (not shown). The resistor 26 may be replaced by a transistor or by silicon controlled rectifiers (Fig. 4, not shown) and the circuit for deriving a control voltage may include a voltage sensitive bridge circuit having a reference Zener diode in one of its arms (Fig. 3, not shown). The exciter arrangements may be of the brushless type.