Development of a 55 kW Diesel Powered Auxiliary Power Unit for Hybrid Electric Vehicles.

Abstract : Three auxillary power units (APU) were developed for military hybrid vehicle applications with funding from DARPA. One APU was for the electric M113 troop carrier originally converted to electric power in the 1960's. The other two APU's developed during this project were for hybrid electric High Mobility Multipurpose Wheeled Vehicle (HMMWV) projects. For this APU design a Volkswagen 1.5-1 diesel engine drives a permanent magnet generator, that with associated inverter produces 55kW of DC power at 380 volts. Overall thermal efficiencies of 33% were observed. The controller for the APU's was based on the personal computer (PC) CPU. Basing the controller on the PC allowed flexibility in meeting the individual requirements of the different vehicles. Given a power level request from the vehicle controller, the APU controller set the engine speed for optimum thermal efficiency. The generator electronics adjusts the voltage and thus the current output from the inverter to deliver the requested power to the vehicle's electrical bus.