Fundamental Studies of a Variable-Voltage Hybrid-Electric Powertrain

Advances in electric propulsion may provide the opportunity to incorporate multiple distributed propulsors through the use of electric drives and electric power transmission at dramatically lighter weights than mechanical drivetrains. While small-scale UAS (0-20lb) have achieved distributed electric drivetrains, the electro-chemical power-sources do not scale and are weight prohibitive for larger UAS and future eVTOL aircraft with practical range, endurance, and payload requirements. An alternative to the electro-chemical powertrain is the hybrid-electric powertrain. In this paper, a variable-voltage hybrid-electric powertrain is designed, constructed, and tested carefully to examine the effects of variable-voltage generators for variable-RPM electric drives. The paper examines the powertrain component by component, with over 370 test points, from a single electric drive to an integrated powertrain with four distributed propulsors, in a fully instrumented test bed.