Approach for Simulating Air Gap Between Armature and Rails Based on the ${A}$ – $V$ Finite-Element Method

Abstract

The armature is usually partly in contact with rails, and in the noncontact portion, narrow air gap exists. It is difficult to simulate such narrow air gaps in the calculation of electromagnetic fields by the ordinary finite-element method (FEM), due to the difficulty of mesh generation inside and around the gap. A novel approach is presented to simulate the gap in this paper, in which the domain of air gap is not built and the conductors (the armature and rail) are made in contact geometrically but not electrically, so that the mesh generation difficulty can be avoided. The noncontact electrically means that with the ${A}$ – $V$ algorithm of electromagnetic field, the electric potential variable $V$ on both sides of the interface between the conductors is made unrelated or discontinuous to achieve the effect that the current cannot go through the interface, while the magnetic vector potential variable $A$ is continuous on the interface, so that the magnetic field is normal or can go through the interface normally. By this novel approach, the air-gap effect can be reflected in the absence of the gap geometrical model, which can offset the defect of the ordinary FEM in the simulation of narrow air gaps. The presented approach is actually an improved FEM with ${A}$ –V algorithm.