High Voltage Turboelectric Testbed Design, Integration, and Performance

Abstract This paper presents the experimental results of a turboelectric aircraft ground test rig representative of emerging electrified aircraft, operating at a system voltage of 550V. Hybrid turboelectric power systems operating at higher voltages increase overall system effectiveness by virtue of their decreased I2R losses and conductor weight. This affords turboelectric aircraft design flexibility as more overall weight and space can be allocated to energy sources. The test rig into which this electrical system was outfitted has been used to analyze system performance in previous work. However, the previous electrical configuration operated at a lower voltage undesirable for use with an engine capable of outputting 180kW. The system discussed in this paper was constructed to achieve two objectives: demonstrate the transient and steady state loads induced on a turbine engine through electric loading, and highlight the considerations necessary to create a high voltage system. These objectives were accomplished through the fabrication of a turboelectric ground vehicle comprised of a modified Cessna-172 aircraft, a modified PBS-TP100 turboprop, an Emrax 228 HV generator, a variable-resistance load, and a purpose-built powertrain. The electrical system is supplied exclusively from the generator coupled to the turboprop through a pulley system, devoid of any supplementation in the form of batteries or capacitance. A test matrix was devised in which the turboprop was incrementally stepped through fixed throttle positions at which the system was placed under varying electric loads. Acquired engine operation data included output shaft torque, free and core turbine shaft speeds, and combustion gas temperature; while voltage, current, and power data was recorded at different locations within the electrical systems. Observations from this study highlight the importance of capacitance to hybrid power-trains, the forces induced on turbine engines by electric loading, and functional safety considerations in the design and operation of high voltage turboelectric systems.