A brushless D-C generator for aircraft use

THE COMMUTATOR has long been a distinctive and sometimes troublesome feature of d-c generators. It functions as a mechanical rectifier converting the alternating armature voltages to direct voltage for the generator load. It is a well-known fact that the rectifying action of the commutator can be performed by static rectifiers if it is economically feasible to do so. In other words, a d-c generator can be replaced by an a-c machine with its output completely converted to direct current by static rectifiers. This has been done infrequently in the past.1,2 Economics and application requirements have seldom justified the added complexity and increased cost. However, in modern aircraft applications a different situation exists. The increasingly severe environmental requirements placed on generating equipment have made it more and more difficult to obtain the necessary reliability and service life from commutator and brush systems. Higher altitudes have necessitated continual improvements in the ability of brush commutator systems to work under low-humidity, high-temperature conditions. In addition, demands for lighter weight generators have resulted in electrical designs which make satisfactory commutation even more difficult to obtain. The logical result of these trends is the elimination of mechanical commutators in certain air-borne d-c generating systems. This paper reports the development of such a system for a modern, high-performance intercepter aircraft.