Transient currents and torques in wound-rotor induction-motors using the finite-element method

The authors describe a time-stepping finite-element technique for modelling transient torques and currents in a slip-ring induction motor. The method is based on a coupled fields and circuit equation approach that allows the winding inductances to be modified to account for certain three-dimensional effects. The numerical solution incorporates a moving rotor so that slotting and saturation effects can be modelled accurately. The method is verified by direct comparison with experimental results obtained from a motor subjected to a supply reconnection at speed. It is shown that the general method can be extended in a straightforward manner to accommodate cage induction motors