Speaker
Description
The development of ultrahigh power density rotating machines is a research priority identified by electric aircraft programs worldwide, including ARPA-E, NASA, Airbus, and many others. The reduction of alternating current (AC) losses of all components in rotating machines is critical to reduce to manageable levels, and AC losses can be the dominant factor affecting the machine efficiency and design viability.
This effort is utilizing a recently developed rotating magnet based isothermal calorimeter (SAM) apparatus to measure AC losses at 77K using liquid N2. The system utilizes the stator slot position of a permanent magnet rotating machine, with Bmax ~ 0.58 T in the airgap and dB/dt of up to 240 T/s. A complex 3D environment of B-fields of varying strength, time-varying direction, and harmonic frequencies is achieved, simulating the environment of a real motor or generator. The maximum sweep rates achieved are up to ~ 60 T/sec, which is about ~ 5x higher than typically achieved by other AC loss test systems.
This device has been used to measure the AC loss of many types of superconductors, including YBCO tapes and cables with varying architectures and Ag and Cu thickness, conductor-round-core (CORC), Roebel, and carpet stacks of varying # layers. Metallic and carbon conductors have also been studied including Cu-litz cables with strand filament diameters of 50 μm and 80 μm, ultra-pure Al 99.999+% with varying sheaths and filaments, carbon nanotubes, and others are planned. The experimentally measured losses are compared to theoretical models, when possible. And the impact of AC losses on the power density and efficiency for rotating machines is analyzed.
Acknowledgments: Support by the Air Force Office of Scientific Research (AFOSR) LRIR # 18RQCOR100, and the Aerospace Systems Directorate (AFRL/RQ)
