Thrust expressions for induction motors with thin conducting secondaries

Using the multilayer approach, formulas are derived for the thrust and normal forces for motors where the secondary consists only of a conducting metal sheet. For these motors, the conventional thrust expression, with the standard goodness factor, does not apply. New goodness factors are calculated and the force expressions thus obtained are cast into a standard closed form. These closed-form expressions are contrasted with the standard ones for motors with normal secondaries, i.e. copper backed with thick nonconducting (laminated) iron. They are also compared to experiments that demonstrate the validity of the method for calculating the thrust via goodness factors