A Method Of Optimal Design Of Single-sided Linear Induction Motor For Transit

The need for industrial application has increased rapidly in the h e a r induction motor (LIM) as a propulsion system. The differences between LIM and ordinary induction motor are the characteristics such as end effect, transverse edge effect, and normal force which are bad influences on LIM performance. Analysis of LIM has been studied and developed by many authors but optimal design of LIM hasn't. [l] [2] Optimal design of LIM is suggested ffom equivalent circuit in 1988 by Nonaka who uses SUMT(sequential unconstrained minimization technique) as well as the space harmonics [3]. He adopted the design variables such as rating slip, pole number, pole pitch, stack height, secondary aluminum's thickness, over hang and slot width to slot pitch. But it is difficult to obtain the optimal design variables of LIM because the ratio of voltage to frequency (V/o, magnetic loading, must be decided by designer's experience. In case of fixed variables adopting the turn number per slot and current density of conductor, the slot height is calculated by the ratio of slot width to slot pitch in order to obtain the cooling area and slot leakage permiance. Accordingly, the improvement of characteristic and decrease of weight is limited in LIM. In this study, the method is suggested that all parameters of transit LIM is determined by only basic specification, rated mechanical output(thrust and velocity), using the equivalent circuit and the optimization technique . When the optimization is carried out, the initial value is given to the slot height and the calculation of exact slot height can be obtained by iteration and convergence of current value in circuit equation. The increase of heat by the leakage reactance and cooling area can be calculated by the slot height.