Integral equation method for analysis of magnetic field and inductance of superconducting alternators

Three-dimensional magnetic-field solutions are obtained for superconducting alternators by a boundary-integral-equation method for two problems involving iron structures. The method is applied to two-pole superconducting alternators with an iron shield enclosing the armature. Either the normal derivative of the magnetic vector or the scalar potential can be used as an unknown function of iron boundaries. In the case of the vector potential, the unknown function is the surface current equivalent to the magnetization of the iron shield. The Fourier expansion is used for the representation of the unknown with respect to the azimuthal coordinates. The harmonic components are independent of one another. The higher harmonic components of the magnetomotive force of the winding currents are smaller and decrease more steeply at a distance from the winding layer than the fundamental. The method is applied to a 6 MVA generator and a 30 MVA synchronous condenser, (both superconducting field windings) with good results