Forces in induction motors with laterally asymmetric sheet secondaries

An analysis is presented for the problem of the sheet-secondary induction motor when the sheet is displaced sideways from a symmetrical position. It is shown that the forces which act on the sheet are decentralising and that the magnitude of these forces and of the changes in propulsive force and winding impedance are dependent on five dimensionless parameters which are functions of the motor´s design and its operating slip. Measurements made on a small linear motor, while indicating that the neglected skin effect and endwinding leakage fluxes can be significant, show reasonable agreement with the analysis. A means of reducing the decentralising force is suggested, and reference is made to a method of achieving lateral stabilisation of a freely suspended sheet.