Design and analysis of practical induction motors

A method to estimate the flux-linkages and parameters of induction motors with skewed rotor bars is presented. The proposed method is based directly on a multi-slice time stepping finite element model, hence the effects of saturation, eddy-current, skewed rotor bars and high-order harmonic fields, can all be included readily in the solution. Special formulas for calculating rotor currents, rotor flux-linkages and air-gap flux in quadrature-phase winding system are deduced. The computed currents and flux-linkages from the finite element model are used directly to compute the parameters of the lumped circuit model with the help of the least squares method. The advantages of the proposed method are its simple physical concept, high accuracy and versatility. The method is suitable to study virtually all modes of operating conditions, including dynamic operations, of induction motors.