Torque calculation with conforming and nonconforming movement interface

This work analyzes the use of conforming and nonconforming movement techniques for torque calculation with high-order hierarchic interpolation in electrical machines thin air gaps. For the nonconforming movement formulation, the Lagrange multipliers are used. The moving band is used for the conforming case. The behavior of torque results as a function of interpolation order and air-gap thickness is discussed. In order to compare formulations, results for two thin air-gap machines are shown

I. Introduction

There are several works about torque calculation while considering the movement, but the use of nonconforming meshes combined with high-order interpolation has not been investigated yet. The aim of this work is to clarify the use of high-order interpolation for torque calculation; in particular, when no constraints are imposed to the rotor displacement. Many papers indicate the use of high-order interpolation to improve the torque accuracy [7]–[10]. These works, however, consider the rotor displacement step equal to the length of an element in the air gap. In other words, there is no deformation of the elements or nonconformity between the meshes. Moreover, the torque is not studied with high-order interpolation for small displacements of the rotor in small air gaps. So this subject deserves more attention. This work demonstrates that if the air gap is thin, the high-order interpolation is not recommended and the first-order one produces better results.