Magnetic field analysis in squirrel cage induction motors

A method for analyzing the field in a squirrel-cage induction motor is discussed, starting from a classical design scheme but using the finite element technique. The approach considered allows the calculation of the flux density distribution in an induction motor at different operating points. A magnetostatic approach is used to model the no-load situation; for the locked rotor situation, a time harmonic solution is used. This leads to the calculation of induced currents, accounting for the real saturation. The parameters deduced from these calculations are influenced by the local saturation, and overall correction factors may be avoided. This approach may be used for all three-phase systems, having a flux pattern that remains virtually the same as a function of time. It is shown that a combination of a correct flux distribution calculation method with appropriate input and output routines may lead to a design procedure which can be used by industrial manufacturers