Comparison of numerical and analytical simulation of saturated zig-zag flux in induction machines

An analytical approach to calculate the saturation of the magnetic field in cage induction machines (IM) is compared with non-linear finite element (FEM) time step solutions and with measurements. Especially at locked rotor the saturation is dominated by the air-gap zig-zag flux, whereas the main flux saturation is of minor importance, especially in non-skewed machines. The analytical approach allows also the calculation of harmonic rotor currents and the tooth flux pulsation at any given slip, which is e.g. used for determination of additional no-load and stray load losses or harmonic torque components. The analytical method allows a much faster solution than the FEM approach with similar accuracy of results.