Nobuo Okumura

Trial Test of Fully HTS Induction/Synchronous Machine for Next Generation Electric Vehicle

Our group has tried to introduce High Temperature Superconducting Technology to electric vehicle (EV) drive motor, and developed High Temperature Superconducting Induction-Synchronous Machine (HTS-ISM). In this paper, 20 kW class HTS-ISM were designed and manufactured with DI-BSCCO wires. First, we developed and tested partial superconducting HTS-ISM (HTS rotor windings with copper stator) for clarification of the performance. We could observe the efficiency at 92.3% even for the light load. Furthermore, we successfully fabricated and conducted no-load test for fully superconducting HTS-ISM. It was verified that stable synchronous rotation at 1200 rpm was succeeded, which is the world-first success of achieving the rotation at over 1000 rpm for fully superconducting motor. Our results are one of the big steps for realizing the HTS-EV.

Controllability of HTS Induction/Synchronous Machine for Variable Speed Control

Our group has been studying a high-temperature superconductor induction/synchronous machine (HTS-ISM). This motor has the same structure as a conventional induction motor. Replacing secondary windings with HTS windings, however, the HTS-ISM has several intrinsic features, i.e., high torque density and high efficiency. In this paper, we established a maximum efficiency control method for the HTS-ISM. This method is based on the electrical equivalent circuit and the optimized excitation condition. We examined the performance of this operation in comparison with the conventional vector control, in which magnetizing current is fixed to be constant. As a result, we found that the HTS-ISMs rotation characteristics were improved by the developed maximum efficiency operation.