Study on High-Efficiency Linear Induction Motor for Transit

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1.Use of linear induction motor with end-effect compensatorWhen the primary member of linear induction motor is restricted to the present length, the only means to solve the problem left for higher efficiency is to compensate the end-effect. It will be the most effective method to use the magnet rotator type of end-effect compensator. The effect and the technique to use are as follow:(1)The overall efficiency of linear motor with the compensator increases by 5% at least and increases to the value of 76%. The overall thrust increases by about 40%. That is, the linear motor with higher-efficiency and high-density thrust can be realized.(2)The two-pole compensator, whose diameter is half and the volume is one forth as compared to the four-pole compensator, has almost the same effect for the compensation. The two-pole compensator can be equipped in the space of 0.2m in front of the primary core of linear motor with the length of 2.5m.(3)In making the magnet pole of compensator formed with plural permanent magnets, the whole of pole should be magnetized in lump sum not to decrease the proper characteristics.2.Use of linear induction motor with long primary member(1)In the conditions that the air gap is 12mm for the safety and the width of secondary conductor is limited to 400mm, the pole pitch is saturated to about 400-500mm though the longer pole pitch increases the efficiency.(2)Large number of poles realize the small operating slip for higher efficiency. The minimum operating slip will be about 0.07 at the schedule speed of 40km/h taking into consideration of the power factor. To obtain the efficiency of 80%, the linear motor with twenty poles and the primary length of 6m is necessary.