Electromagnetic redesign of nasa’s high efficiency megawatt motor

Thomas T. Tallerico, Justin J. Scheidler, Dongsu Lee, Kiruba Haran

Research output: Chapter in Book/Report/Conference proceedingConference contribution


NASA’s high efficiency megawatt motor (HEMM) is being developed to achieve the performance needed by single aisle class electrified aircraft. It is a 1.4 MW electric machine designed as a generator for NASA’s STARC-ABL concept vehicle. It has performance objectives of greater than 16 kW/kg electromagnetic specific power and 98% efficiency. A significant flaw in the preliminary electromagnetic design of HEMM was recently discovered. The stator teeth in the preliminary design would have caused the magnetic flux in the rotating components of HEMM to oscillate at a very high frequency (12,240 Hz). Two independent energy loss analyses are presented to show that the frequency of this oscillation would have been high enough to cause eddy current losses that significantly exceed the rotor’s loss limit (51 W), despite the very small magnitude of the oscillation (<0.01 T). To eliminate these rotor losses while continuing to meet the target performance, it was determined that the stator teeth needed to be removed and the electromagnetic geometry of the motor needed to be revised. The revised, slotless HEMM design is summarized. Also presented is a sensitivity analysis of the new design to key unknown variables such as the temperature of and number of turns in the superconducting rotor coils and the stator winding’s average temperature.

Original languageEnglish (US)
Title of host publicationAIAA Propulsion and Energy 2020 Forum
PublisherAmerican Institute of Aeronautics and Astronautics Inc, AIAA
Number of pages15
ISBN (Print)9781624106026
StatePublished - 2020
EventAIAA Propulsion and Energy 2020 Forum - Virtual, Online
Duration: Aug 24 2020Aug 28 2020

Publication series

NameAIAA Propulsion and Energy 2020 Forum


ConferenceAIAA Propulsion and Energy 2020 Forum
CityVirtual, Online

ASJC Scopus subject areas

  • General Energy
  • Mechanical Engineering
  • Aerospace Engineering
  • Electrical and Electronic Engineering
  • Control and Systems Engineering


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