A SIMPLE AIRCRAFT ELECTRICAL SYSTEM USING CHANGEOVER CONTACTORS.
ROYAL AIRCRAFT ESTABLISHMENT FARNBOROUGH (UNITED KINGDOM)
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A non-paralleled aircraft electrical power system is described, which, while avoiding the complexity of a paralleled system, does not suffer from supply interruptions of long duration which are liable to occur with conventional non-paralleled systems. The system comprises two generators, which cannot be connected in parallel, two normally closed changeover contactors and protective devices such that supply interruptions for all but the rarest of faults are significantly shorter than 100 milliseconds. Among these protective devices is a novel form of undervoltage protection, in which rapid operation is achieved by eliminating the time delay previously used to discriminate between transient and sustained undervoltages. The use of this type of changeover contactor results in an exceptionally simple system since it eliminates the bulk of the logic elements which are required for a conventional system using single way contactors. No single fault, apart from one in the immediate vicinity of the load distribution point or busbar, results in the permanent loss of any part of the load. Author