High Power Density Induction Motors and Drives for Aircraft Propulsion

We are pursuing the development of a new induction motor through innovative design with embedded drives enabling advanced electric drive technology to meet aircraft propulsion needs. The Phase II will continue to focus on the design improvements started in the Phase I: (1) power loss and cooling and (2) electric drive integration, and will also include the building and testing of a prototype motor and drive system. In this work, we have avoided the use of a permanent magnet (PM) based motor arrangement, which of course, would contain NdFeB magnets. Our concept incorporates an asynchronous (induction) style motor with embedded inverters and a two-phase semi-evaporative cooling system. Our total system (motor and drive) ultimately targets a continuous power density of 10 kW/kg and 12.6 kW/L or greater. The motor and inverter design is based on two novel technologies and related controls for electric motors that have yielded record torque density and power density. The first novel technology is Variable Cross-Section Wet Coils (VCSWC) that configures the conductor windings with integrated cooling. The second technology is the integrated electronic drives, which are cooled as part of the same circuit that cools the stator, and which makes the full system very compact.Based on the results of the Phase I the proposed electric motor to be built in the Phase II should be a 2 MW, 5000 RPM machine that represents a number of advances over the extant OSU record-breaking induction motor, and will be a world record winning motor with double the torque and an increased power density (25% improvement to12.5 kW/kg, continuous) with, at the same time, an increased efficiency (98.5%, cruise).The Phase I/Phase II electric motor has an increased number of conductors per slot, and this is a key to loss reduction and increased efficiency. The Phase II will be focused on a design optimization within these basic parameters, and then a build and test program. In this Phase II program we are pursuing the development of a new induction motor design with embedded drives which enable advanced electric drive technology to meet aircraft propulsion needs. Our concept incorporated an induction style motor with embedded inverters and incorporates two-phase semi-evaporative cooling. We are targeting a continuous power density of 10 kW/kg (motor + drive) and 12.5 kW/kg (motor only) by re-optimizing an existing design for higher excitation and lower losses.   The motor and inverter design is based on two novel technologies and related controls for electric motors. The first novel technology is Variable Cross-Section Wet Coils (VCSWC) that configures the conductor windings with integrated cooling. The second technology is the integrated electronic drives, which are cooled as part of the same circuit that cools the stator. This approach is paired with a tuned coil strategy to reduce losses. The high levels of cooling allow both a higher current loading as well as a lower loss operation of the winding, which drives both power density and efficiency. The overall objective of the program is to develop a new induction motor design with high power density (> 10 kW/kg and 12.6 kW/L, continuous, system level) and 12.5 kW/kg motor only, as well as embedded electronic drives for aircraft propulsion. The Phase I proposal successfully focused on design improvements in two areas, (1) loss and cooling, and (2) design for electric drive integration. The Phase II will complete the design and optimization of the specified motor, followed by building and testing the motor.   Based on the results of the Phase I the proposed electric machine to be built in the Phase II should be a 2 MW, 5000 RPM continuous duty motor that represents a number of advances over the extant OSU record-breaking induction motor, and will be a world record winning motor with double the torque and an increased power density (25% improvement to 12.5 kW/kg, continuous) with, at the same time, an increased efficiency (98.5%, cruise).   Deliverables: Complete motor design concept that meets power density and target specifications. Complete optimized 3D model of motor. Complete design with detailed assembly drawings and with bill of materials for parts and tooling. Complete optimized simulation of the motor drive control mounted on the stator. Assemble 2 MW electric motor and drive. Complete testing of motor and drive, including calibration.

In addition to electric passenger aircraft, NASA can benefit from these high power density induction  motors because of low cost, and high efficiency for space applications.  Because these motors do not use permanent magnets,  in the future NASA can avoid shortages of motors due to lack of availability of permanent magnet materials These low cost, high efficiency induction motors can be used in passenger aircraft (eVTOL, 4-40 passenger aircraft, 40-400 passenger aircraft), trucks, trains, ships, and cars.   Because these motors do not use permanent magnets,  in the future commercial customers  can avoid shortages of motors due to lack of availability of permanent magnet materials

This is early/mid-stage (TRL 4) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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