Asymmetrical constants and effect of joints in the secondary conductors ofa linear induction motor

In this paper, one method of identification of the Linear Induction Motor ( LIM) constants is presented. Beside the asymmetrical nature of the LIM's co nstants (because of finite winding lengths) it was noticed that when a join t in the secondary conductor moves inside the active area of the LIM it cre ates variation and fluctuation of the secondary resistance of the LIM. The variation and fluctuation of the secondary resistance affects the thrust of the LIM which also fluctuates. These fluctuations of the thrust are not ac ceptable in some applications such as Linear Motor Elevators in which the r iding comfort is very demanding. A hardware solution to diminish the fluctu ations of the thrust is proposed. It consists of adding a secondary joint a t half pole pitch distance from the primary joint. This second joint create s another fluctuation that opposes the fluctuation caused by the primary jo int. Thus, the secondary joint cancels the fluctuation effect caused by the primary joint. Several experiments were performed to confirm this solution .