Accurate sub-domain model for magnetic field computation in electrical machines with HTS materials

Abstract

The primary aim of this study was to develop and validate an accurate sub-domain analytical model to estimate the magnetic field of electric machines with high-temperature superconducting (HTS) excitation and armature windings. The model was developed by utilizing the separation variable and harmonic analysis methods to solve Laplace's or Poisson's equations of the vector magnetic potential in two-dimensional polar coordinates. The theoretical derivations of the final analytical equations for the magnetic flux density distribution in the air-gap and in permanent magnets, electromagnetic torque, and no-load backelectromotive force (back-EMF) are explained in detail. Finally, the magnetic vector potential, flux density distribution of each sub-domain, noload back-EMF, and inductive reactance of the armature winding were solved by considering the critical parameters of the superconducting materials, and the influence of higher harmonics. The finite-element method (FEM) was used to validate the accuracy of the developed analytical method for the investigated HTS generator. The results show the developed analytical method is accurate and time-saving.