Compensation method for end effect of linear induction motor

Abstract

For the end effect of linear induction motor (LIM), the authors propose a new concept that the end effect can be compensated only by the supply of secondary current synchronized with the current of LIM in front of the entry end of LIM, without considering with the flux density distribution in the LIM primary region. As a concrete method to supply the secondary current in front of LIM, the authors propose the rotator with rare-earth type permanent magnets which has strong flux density without ohmic loss, and does not cause the power factor problem even for the influence of end effect. The results of analytical study on the numerical example of LIM designed for subway are as follows. This method can make the flux density and thrust density distribution in the LIM primary region almost agree with those of the case without end effect. This method can compensate the thrust, power factor, efficiency of LIM at the rated speed to coincide with the characteristics without end effect. There is no problem in the slip characteristic curves of LIM with the compensator, although the compensator only rotates synchronizing with the frequency of LIM. The effect of compensation becomes large in the lower slip. The force to rotate the compensator is very small in the suitable design.