Coupling the circuit equations to the non-linear time dependent field solution in inverter driven induction motors

The conventional way of analysing electric machinery has been to impose currents or current densities, to calculate from them the electromagnetic field and from that the self and mutual inductances of the windings. Circuit equations using these inductances would give correct values for the currents in the windings. In this paper, the field and circuit equations are coupled, giving a time dependent set of nonlinear equations, the solution of which gives the magnetic vector potential at every point in the cross section of the machine and the electric field intensity at the cross section of the conductors. The method is of particular interest when the harmonic content of the excitation is large, prohibiting the calculation of permeability of iron from only the fundamental.