1. School of Electrical Engineering, Key Laboratory of Magnetic Levitation Technologies and Maglev Trains, Ministry of Education of China, Southwest Jiaotong University, Chengdu, Sichuan 610031, China
2. Superconductivity and New Energy R&D Center, Southwest Jiaotong University, Chengdu, Sichuan 610031, China
3. College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics (NUAA), Yudao Street 29, 210016 Nanjing, China
4. Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
5. Oil Testing and Perforating Company of Daqing Oilfield Limited Company, Daqing, Heilongjiang 163000, China