Three-dimensional quasi-static magnetic field in superconducting-rotor synchronous generators with a magnetic steel rotor screen

A 3-dimensional numerical finite-difference method, incorporating the nonlinearity of the magnetic material, is used to calculate the field in and around the magnetic steel rotor screen of two synchronous generators with superconducting rotor windings. One machine is a small experimental model being used to investigate some of the problems of superconducting generators and the other is based on an outline design of a large 1300 MW machine. The field has been calculated on both open-circuit and full load for the latter. The flux density inside the rotor screens is, for the most part, displayed in the form of relative permeability profiles on various planes and cylindrical surfaces because this information can be used to assist in the later solution of the eddy-current screening and damping performance. The finite-difference method used is block successive overrelaxation, each block being formed by the potentials on a given r, ¿ plane perpendicular to the axis of the machine.