Time-harmonic finite-element analysis of eddy currents in the form-wound stator winding of a cage induction motor

A finite-element model for calculation of eddy-current and circulating current losses in a multi-conductor stator winding of a cage induction motor is presented. In this model, the eddy current formulation of the series and parallel connected stator bars is solved together with the circuit and field equations using a two-dimensional time-harmonic approximation. The Newton-Raphson method is applied to solve the total system of nonlinear equations. The finite-element mesh is discretised finely enough in order to take the phenomena correctly into account. The eddy-current loss distribution of the stator bars and the quantitative results of eddy-current and circulating current losses have been studied with two different conductor arrangements inside the stator slots. The results show that the eddy-current loss in the stator winding is one of the most significant loss components. They also show that the radial position of the stator bars has a remarkable effect on the losses. The radial flux that passes through the stator bars can be guided to stator teeth by using magnetic slot wedge material to reduce the eddy-current loss.