Nonlinear complex finite-element analysis of squirrel cage induction motor performance

The application of complex analysis and the finite-element method for predicting the performance of a three-phase squirrel cage induction motor under a sinusoidal voltage-forced operation is described. The field region is discretised by triangular elements and the Galerkin approach is employed to solve a nonlinear complex Maxwell equation. Core saturation and the induced rotor bar currents are considered in the analysis. The induced back voltage and inner impedance in the equivalent circuit are obtained, based on the obtained field solution. The stator current is then iterately determined by using the fixed phase voltage and the external and inner impedances. The stator current, torque and power factor were obtained as functions of the line voltage and the slip. An experiment using a 1 HP squirrel-cage motor operating at several line voltages supplied by a 20 kVA balanced three-phase transformer was tested to verify the calculated results