[1] Southwest Jiaotong Univ, Sch Elect Engn, Chengdu 610031, Peoples R China
[2] Southwest Jiaotong Univ, Sch Elect Engn, Chengdu 610031, Peoples R China
[3] Southwest Jiaotong Univ, Key Lab Magnet Suspens Technol & Maglev Vehicle, Minist Educ, Chengdu 610031, Peoples R China