Forces in thin-plate linear reluctance motors

An analytical model is presented for linear reluctance motors (LRM) with thin-plate secondaries where the plate is magnetically saturated in normal operation. Finite-element field modeling confirms that the plate has regions of nearly constant magnetization which can be represented by equivalent surface currents. The model correctly predicts the variation of force with current for a load-angle of 45°; the greatest discrepancy is only 6%. The model overestimates the change in the normal force with load-angle, with maximum errors of +14% at a load-angle of 0° and -24% at a load-angle of 90°. Preliminary measurements from an experimental machine gave similar results. The forces in the model are almost linear functions of current, whereas the forces in a conventional LRM vary with square of the current