Analytic Calculation of Eddy Currents in the Slots of Electrical Machines: Application to Cage Rotor Induction Motors

This paper describes a two-dimensional analytic model for predicting the induced currents within conducting material placed in the slots of electrical machines. Slot-embedded conductors are subjected to a rotating magnetic field including space harmonics. The analytical method is based on the resolution of time-harmonic homogeneous Helmholtz´s equation in polar coordinates by the separation of variables method. The global solution is obtained using boundary and continuity conditions between the different sub-domains (rotor slots and air-gap). The proposed model is applied for magnetic field and torque calculations in a rotor cage induction motor under steady state condition. The analytical results are verified with those obtained from finite element analyses.