An axisymmetrical finite element-boundary element coupling method for the study of circuit breakers

Rotating arc circuit breaker modeling requires the computation of the magnetic induction on the arc in order to estimate the Laplace force. An accurate modeling has to take into account the eddy currents and the magnetic saturation in axisymmetrical geometry. A finite element-boundary element coupling method is considered to deal with open boundary problems. Finite element domains can be used for conducting and nonlinear magnetic materials while boundary element domains are used elsewhere, that is mainly for the air. Numerical stability of the finite element method is insured by the use of an auxiliary potential equal to the vector potential divided by the radius. Boundary integrals required by the BEM involve elliptic functions which prevent any analytical treatment. Numerical integrations are made by an adaptative scheme which provides good accuracy of results. As the nonlinear character of the system prevents the use of complex formalism, even for sinusoidal excitations, transient analysis is made by using an Euler implicit scheme for time integration. The computed induction provides the time evolution of the force acting on the arc