Relation between Electrical Characteristics and Size of Linear Induction Motor for Urban Transit

Abstract

The linear induction motor (LIM) has been used as the driving device of urban transit vehicle with maximum speed of about 70km/h in Canada and Japan. The relation between the efficiency or the kW/kVA and the length of primary member of LIM are analyzed by using many design examples satisfied the specifications of rated speed of 11m/s, thrust of 11kN, mechanical clearance of 12mm and line to line voltage of three-phase of 1, 100V. The efficiency increases with motor length and saturates with length to the value of about 0.8. The small increase of efficiency requires extremely increase of motor length in the region above the efficiency of about 0.75. The other side, the LIM with relative low efficiency of about 0.65 can be realized with compact size of 1.6m. Both of the use of copper secondary conductor and the shortening of mechanical clearance are used but they are a little effective to improve characteristics of efficiency and kW/kVA.