AC Motor-starting for aircraft engines using APU free turbine driven generators

摘要

The invention is an electric starting system for starting aircraft jet engines (32), (34) and (36) using an APU (10) free turbine driven generator (12). The operating power factor of the starter- generator (12) is controlled during start mode operation of the APU (10) by monitoring the line current via a current transformer (58). Contactors (14) and (16) connect the generator (12) into the aircraft's ac power system and ac starting system, respectively. A master start relay (22) is provided, and is closed in the `start` mode such that a power electronics inverter (24) may be powered from external power via contactors (18). The variable- voltage/variable-frequency output of inverter (24) is controlled via a logic controller (26) and can be applied sequentially to the three engine driven generators (32), (34) and (36) via start relays (42), (44) and (46) to start the engines (32), (34) and (36) respectively. An alternative embodiment of the APU generator/power electronics/starter- generator start system is the utilization of a separate induction motor starter than can operate with or without the use of power electronics.