Electromagnetic Analysis of Fully Superconducting Motors Employing Dilute Gas Rotor Cooling and Liquid Hydrogen Stator Cooling Structure

Nov. 30 10:30-11:00

*Yutaka Terao1, Kazuki Akasaka1, Hiroyuki Ohsaki1, Keiichi Okai2, Hideyuki Taguchi2
The University of Tokyo1

Aviation industry has accelerated effort to reduce greenhouse gas emission based on the statement of ATAG (Air Transport Action Group); Targeting Net Zero of CO2 emission by 2050. One of the solutions to achieve this statement is electrification of aircraft propulsion systems.
Fully superconducting rotating machines (FSCMs) are one of the most effective solutions for realizing high-power density machines applicable to electric aircraft propulsion systems. This is because, superconducting field/armature windings have high current density at ultra-low temperature and can generate higher magnetic field. Therefore, weight of windings and iron can be reduced and then, light weight motor/generators are available. So, the authors have been proposing the FSCMs using two kinds of superconducting windings; MgB2 armature windings and REBCO field windings [1, 2].
However, the cooling structures for the FSCMs tend to be complicated because both armature and field windings demand coolant, refrigerators and so on.
In such a technical challenge, the authors employed cooling method using dilute gas as well as liquid hydrogen [3]. While the MgB2 armature windings are cooled at 20 K via liquid hydrogen, the REBCO field windings are operated below 50 K with heat conduction and convective heat transfer via dilute gas. This structure contributes to simplifying the rotor cooling structure.
In this study, the authors conducted electromagnetic design of the FSCMs via finite element method (FEM) with considering not only active material parts but also important structural parts. And based on these analysis results, motor output density, losses, and so on are evaluated and discussed.

[1] Y. Terao, W. Kong, H. Ohsaki, H. Oyori and N. Morioka “Electromagnetic Design of Superconducting Synchronous Motors for Electric Aircraft Propulsion,” IEEE Transactions on Applied Superconductivity, Vol. 28, no. 4, pp. 1-5 (2018).
[2] Y. Terao, Y. Ishida, H. Ohsaki and H. Oyori, “Electromagnetic Characteristic Comparison of Superconducting Synchronous Motor Characteristics for Electric Aircraft Propulsion Systems,” SAE International Journal of Advances and Current Practices in Mobility, Vol. 2, pp. 828-837, (2019).
[3] M. Kato, Y. Terao, and H. Ohsaki, "Analytical and experimental study on the feasibility of rotor cooling with thin gas for fully superconducting rotating machines," Journal of Physics: Conference Series, Vol. 1857, No. 1, p. 012016, 2021.

Keywords: Dilute gas, Electric aircraft, Fully superconducting motors, Liquid hydrogen