Electric power supply plant, in particular for an air conditioner in a railway coach

摘要

929,199. Automatic control systems. BETEILIGUNGSUND PATENTVERWALTUNGS G.m.b.H. Oct. 20, 1961 [Oct. 22, 1960; July 26, 1961], No. 37741/61. Class 38 (4). In an A.C. generator 2 which may be driven at a variable speed and which supplies a load 4, e.g. an induction motor for an air-conditioning plant in a railway coach, the exciting current flowing through the field winding 7 is arranged to be increased when the terminal voltage drops because of variation in the load, the arrangement being such that variations in voltage due only to speed variations do not affect the field current. As shown, the terminal voltage of the generator 2 feeds a circuit including a reactor 5 and a rectifier 6. The reactor 5 has an inductance which remains substantially constant over a wide frequency range, and it is shown that the current flowing through 5, 6 is independent of the frequency whilst the effective field flux remains constant. The voltage across the rectifier 6 is applied to a resistor 18 in opposition to a constant voltage derived from a battery 8 feeding the winding 7. When the load 4 is connected in, the effective generator field flux is reduced and the current flowing through 5, 6 is reduced, so that the effective voltage applied to the field winding 7 is increased. The generator excitation is thus increased, and the terminal voltage rises to a value which, at the particular frequency, corresponds to the noload value. Variation in the frequency without a variation in the load remains without any influence on the current flowing through the regulator. The difference voltage may be amplified (Fig. 2, not shown) before being applied to the winding 7. The circuit may include transistors or controlled rectifiers and Zener diodes, and examples of such arrangements are given (Figs. 3 to 6, not shown).