Unified theory of superconducting and PM synchronous machines

It is shown that the electromagnetic theory of the superconducting AC machine is very close to that of the surface-magnet permanent-magnet synchronous machine. Methods for calculating the EMF and synchronous inductances are practically identical and almost interchangeable. It is not only possible to use related algorithms for design calculations, but the results are readily compared in a form convenient for studies, especially of very large machines. The theory includes not only the steady state but also the subtransient state following a short-circuit fault. Methods for analyzing the demagnetization of permanent magnets, or the quenching of the superconducting winding, are closely related. The paper describes all the main points of the theory with numerical and graphical illustrations.