Study on designing high current density rotor windings of superconducting generator and relation of the stabilities in static and rotating conditions

It is critically important to realize high current density superconducting rotor windings to make the superconducting generator economically competitive to a conventional one. High current density rotor windings inevitably suffer from instability problems. Therefore, the rotor windings should be designed for the quench currents to surely exceed the maximum operational currents in the rotating condition. In the next step of the Super-GM project, the current density required is 30% higher than that of the rotor winding developed in the former Super-GM project. To test the stability of the rotor windings, usually quench tests are conducted in a static and pool-cooled condition for the simplicity of the test but presently the relation between the stabilities in the static and rotating conditions is not clear. In the paper, we study what information can be obtained and how the stability in the rotating condition can be estimated from the static test. Based on this study, we investigate a method to design quench currents of high current density rotor windings to exceed a required value and discuss what level for the quench current to exceed in the static condition to satisfy the requirement in the rotating condition.