Exciter armature reaction and excitation requirements in a brushless rotating-rectifier aircraft alternator

IN MODERN high-speed high-altitude aircraft, commutation and brush wear become critical problems in the exciters of synchronous a-c generators. To overcome these problems, brushless rotating-rectifier a-c generators have been developed.1,2 In this type of machine, the commutator and brushes are completely eliminated, along with their associated problems. The design engineer, however, is faced with a new problem. He must design an exciter which is an a-c generator loaded by a rotating rectifier feeding a highly inductive load: the main generator rotating field. The rectifier acts somewhat as a rotating switch, switching the load current from one phase to the other. The nonlinear load then presents design problems: What is the effect of this load on exciter armature reaction, terminal voltage, and power factor? The purpose of this paper is to answer this question. A method of calculation is outlined to convert a given d-c rectifier load to an equivalent a-c load. With the equivalent a-c load known, the generator designer can use conventional formulae to design an optimum exciter and regulator system for a given application.