3D modeling of electromagnets fed by alternating voltage sources

A method allowing 3D simulation of AC voltage driven electromagnets is described. Since the harmonic current in the exciting coil depends on the air gap width, the electromotive force in the windings has to be taken into account. A computation method based on the finite element method was developed in order to obtain the static attractive force characteristics of AC electromagnets used for circuit breakers. This method is based on nodal finite elements and loop equations of the electric circuit. Both magnetic field and electric circuit equations are solved simultaneously in the frequency domain. Computation results are compared with measurements on a 32-A contractor/circuit breaker