NASA's X-57 High Lift Motor Controller: Detailed Design, Test Results, and Outcomes

NASA's X-57 High Lift Motor

Controller: Detailed Design, Test

Presentation Title

Results, and Outcomes

Susanah Kowalewski et al.

NASA Glenn Research Center (GRC) Author Company/Organization st AIAA/IEEE Electric Aircraft Technologies Symposium (EATS), July 31 , 2024 This is a work of the United States Government authored as part of the official duties of employee(s) of the National Aeronautics and Space Administration. No copyright is Conference Name, Conference Dates claimed in the United States under Title 17, U.S. Code. All other rights are reserved by the United States Government. Any publisher accepting this work for publication Conference Location acknowledges that the United States Government retains a nonexclusive, irrevocable, worldwide license to prepare derivative works, publish or reproduce the published form of this work, or allow others to do so, for United States Government purposes.

Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.

Distributed Electric Propulsion (DEP)  X-57 Maxwell uses a DEP architecture  Benefits in aerodynamics, control, and reliability  12 high-lift motors (HLM) and controller/converters (HLMC)  Does not increase pilot workload substantially

High Lift Motor Controller (HLMC) Key Objectives  14 kW Output  <330 W of loss  >97% Efficiency  Mass ≤ 1kg  Passive, Outer Mold Line Cooling  Fiber Optic Ethernet  Rapid Software Development

HLMC Thermal and Mechanical Design  Radially mounted MOSFETs  Two isolated heatsinks – conform to outer mold line and provide mechanical support  COTS heat pipe on secondary heatsink  Thermal copper layers internal to circuit boards

HLMC Electrical and Mechanical Design  3 circular printed circuit boards (PCBs)  Minimal inductance between the MOSFET driver and gate  Low coupling capacitance between high power and low power electronics

HLMC Electrical Design  DC bus filter  Silicon Carbide (SiC) MOSFET switches  Optically isolated gate drivers  Fiber optic ethernet  TI Delfino microprocessor  Code generation

HLMC Power and Efficiency Testing  Motor testing with propeller and dynamometer loads  Full power (14 kW) reached with 98.3% efficiency  Less than 330 W of loss from 6 – 14 kW output

HLMC Qualification Testing

Vibration Shock Static Thermal 10.9 Grms DO-160 Sec. 7 16 – 20 Thermal Cycles

 Random vibration test

20 min each axis 6 g > 95% Defect Precipitation

 Shock test 10 Hz – 2 kHz 11 ms pulse -40 to +60 ° C Air

Low power operation Low power operation Low power operation at

 Thermal cycle test

after each axis after each axis extreme temperatures

HLMC Wind Tunnel Testing  High power testing  Passive nacelle heatsink  20 to 50 m/s free- stream air velocity  +60 °C air operation  15,000 ft altitude

Lessons Learned - Mechanical

 Use 3D CAD to ensure fit between PCBs and mechanical hardware  Considerations when affixing MOSFETs to the heatsink:  Ensure the heatsink surface is flat with no sharp edges  Do not over-torque MOSFET screws as it will damage the MOSFET and cause more potential for protrusions through thermal interface material  Vibrations can cause MOSFET screws to loosen if thread locker is not used (even in lab unit). Loose screws will lead to MOSFET over-temperature failure.

 Any “large/heavy” PCB parts should be staked with epoxy to prevent breakage during vibration

Lessons Learned - Electrical

 Use LC filters on low voltage microcontroller supply pins  Isolate high and low voltage electronics to reduce the impact of noise  Use optical coupling electronics where possible  Minimize coupling capacitance of isolated components  Create no-copper zones through all layers of a circuit board at boundaries  Minimize inductance in the MOSFET gate by keeping trace lengths short  Tune desaturation over-current protection for the MOSFET current limit  Use sufficient DC bus filtering capacitance to reduce ripple  Ensure proper clearance in the PCBs for the voltage level at altitude

Conclusions  NASA GRC has developed a flight-weight highly configurable motor controller that can power 3 phase, 14 kW motors.

 The knowledge gained through this integrated approach to electronic power train design has been used as a guide for ongoing new electric power train component development.

Acknowledgments  This work is supported by the NASA Flight Demonstrations and Capabilities Project - X-57 Maxwell and performed at NASA Glenn Research Center (GRC).

 Thank you to NASA Armstrong Flight Research Center (AFRC) and NASA Langley Research Center (LaRC) for their support of GRC in this accomplishment.