INSTANTANEOUS OVERVOLTAGE PROTECTION FOR AIRCRAFT A.C. GENERATORS.

Overvoltage protection in current use on aircraft a.c. systems incorporates a substantial time delay to avoid unwanted tripping with transient voltage rises due to switching etc. Consequently, on the occurrence of a genuine fault, consuming equipment is subjected to an excessive voltage for a considerable time before the fault is cleared. By making overvoltage protection depend on the direction of the change of alternator excitation current as well as on the voltage level, overvoltage faults may be cleared with no deliberate time delay and with no danger of inadvertent operation due to load switching or fault clearance. The circuit and testing of such a form of overvoltage protection are described. Author