Analytical Model of Magnetic Field Generated by Racetrack Superconducting Excitation Winding Within Cylindrical Ferromagnetic Boundary Based on Mirror Method

Since the racetrack excitation windings of the superconducting synchronous motor are in the cylindrical air gap, during the preliminary design, the magnetic field analysis model of the motor can be simplified to solve the magnetic field generated by the current-carrying conductor within single or two circular ferromagnetic boundaries. Because the magnetic field analysis method based on the Laplace equation and Poisson equation is difficult to calculate the flux density on the excitation windings, an analytical model of the superconducting excitation field based on the mirror method is proposed in this article. The calculation results show that the proposed model has high accuracy and computational efficiency for the superconducting synchronous motors, so it is suitable for the preliminary design and optimization of the superconducting synchronous motors. Considering the saturation of the rotor core, a calculation method of the equivalent image current on the rotor core is presented, which can effectively reduce the error of the analytical model in the saturated case. In addition, to make the critical current calculation results of the 2-D model more reliable, a margin factor is added when applied to the preliminary design of superconducting motors.