Fundamental design and electrical characteristics of superconducting commutatorless motor

AbstractSince there are no iron cores in the rotor and stator windings of superconducting synchronous motors, some reactances are intrinsically smaller than those of conventional motors. Thus the low synchronous reactance would be expected to improve the torque‐ampere ratio stability and the overload capacity in case of the variable‐speed drive system of a load‐commutated inverter due to the small armature reaction. Moreover, the low subtransient reactance may contribute to lessen the voltage stress during the shortened commutating period, especially in current source‐type inverter (CSI) systems.In this paper, after presenting analytical formulas needed for a machine design, one design algorithm is described, citing one example of an experimental CSI‐fed superconducting motor of 30 kVA which will be fabricated. Further, the distinguished features in its operation, as expected in the foregoing, are verified by the computer simulation study in comparison with a conventional machine in terms of a high specific power density, an extension of stable power limit, and so on.