The causes and consequences of phase unbalance in single-sided linear induction motors

Unbalance in the phase currents of a single-sided linear induction motor (LIM) under balanced voltage operation is due to asymmetry of the primary windings and to the longitudinal end effect. Two methods of evaluating phase unbalance are presented. The first is analytical and is based on an equivalent circuit model. The second approach is numerical and uses the finite-element method. Computational results are validated by comparison with test results on a large-scale single-sided LIM. It is shown that phase unbalance produces a reduction in both thrust and normal forces, but this effect is likely to be significant only for high-speed LIMs.>