Abstract Body

Currently, the demand for aircraft is on the rise worldwide, and at the same time, there is a growing movement to promote decarbonization by replacing fossil fuel engines with electric propulsion. Therefore, we have been developing a superconducting motor with high efficiency, high output, and low weight. There are two issues we focused on.

The first is the shape of the field coil. REBCO wire, which is widely used in high-temperature superconductivity, is tape-shaped, and the easiest way to wind the wire is to use a racetrack coil. However, in that case, the field coil and the motor shaft will come into contact, so it is necessary to divide the shaft. This raises concerns about the mechanical durability of the motor itself. To solve this problem, we introduce a saddle-type coil and aim to design a coil shape that realizes a single continuous through-axis. A 3D model of the end of the coil that does not apply a load to the wire is created by assuming the coil winding to be a curved surface using the Frenet-Serre formula in the field of mathematics. This method is used in the field of accelerators. By improving durability, it is possible to expect an increase in output due to higher rotation speeds and a reduction in weight due to the saving of parts.

The second is that it is difficult to form an ideal magnetic field distribution when introducing a saddle coil. If it is a rotating field type motor that uses an iron core, the winding can be wound directly around the iron core. As a result, multiple coils form similar magnetic fields, which can be superimposed to form one large magnetic pole. However, in the case of a saddle coil, the coils are arranged on the circumference, and the magnetic field generated by each coil is different. Due to the interaction, it is possible that the magnetic field distribution is far from the ideal, and the output is expected to decrease. Therefore, we aim to generate an efficient magnetic field distribution and achieve a target output of 2 MW through a parameter survey. Specifically, the conditions of the armature (current, number of turns, shape) were fixed, and the analysis was performed by dividing into three cases. As case 1, the total number of turns of the field coil was fixed, and the magnetic field distribution and output were compared by changing the number and arrangement of the coils. As Case 2, we judged that there was still room for output improvement as a result of Case 1, so we aimed to improve output by fixing the coil arrangement and increasing the number of turns. As Case 3, we fixed the number of coils and turns and confirmed the change in output when the coil pitch was shortened.

References

・B.Auchmann & S. Russenschuck, March 2004, Coil end design for superconducting magnets applying differential geometry methods
・Kiyotaka Uyeda, Kohsaku Shimizu & Masakazu Sunada, April 6 1990, Current Situation of R & D on Superconducting Generator

Acknowledgment

This paper is based on results obtained from a project subsidized by the New Energy and Industrial Technology Development Organization (NEDO).