A high temperature superconducting induction/synchronous motor with a ten-fold improvement in torque density

Abstract

In this paper, enhancement of torque density in high temperature superconductor (HTS) induction/synchronous machine is experimentally and theoretically investigated by the use of Bi-2223 windings. Basic structure of this machine is the same as that of a conventional squirrel-cage induction motor, and the secondary windings are replaced by the superconducting tapes. Firstly, quantitative values of the enhanced torque are measured in an experiment using a fabricated motor at 77 K.Then, such torque result is theoretically confirmed based upon the analytical expression, which is derived from the nonlinear electrical equivalent circuit. It is shown that the theoretical result and experimental one agree well each other, and then the torque value drastically increases for more than ten times compared to the conventional induction motor. These results indicate that the compact sized high efficiency HTS motor is possibly realized in simple structure.

Potential for Torque Density Maximization of HTS Induction/Synchronous Motor by Use of Superconducting Reluctance Torque

“…The basic structure of our machine is the same as that of the conventional squirrel-cage induction motor, and excellent characteristics such as high-efficiency synchronous rotation can be realized by the use of HTS windings [3]- [6]. Followed by the fundamental study [3]- [6], high torque density more than at least ten times larger than that realized by the conventional (normal conducting) motor has been succeeded directly through the experiment [7]. For example, in [7], the HTS squirrel-cage rotor windings are fabricated by the use of the commercial rotor core (stator: conventional copper windings; original rated slip torque: 7.9 Nm), and then, such motor can generate "synchronous torque" more than 80 Nm at 77 K. Based upon the aforementioned success, a 20-kW class prototype motor has recently been developed and then succeeded in testing [1], [2].…”

“…Followed by the fundamental study [3]- [6], high torque density more than at least ten times larger than that realized by the conventional (normal conducting) motor has been succeeded directly through the experiment [7]. For example, in [7], the HTS squirrel-cage rotor windings are fabricated by the use of the commercial rotor core (stator: conventional copper windings; original rated slip torque: 7.9 Nm), and then, such motor can generate "synchronous torque" more than 80 Nm at 77 K. Based upon the aforementioned success, a 20-kW class prototype motor has recently been developed and then succeeded in testing [1], [2]. One of the most important targets for the abovementioned R&D project is the maximization of its torque density.…”

New coil configurations with 2G-HTS and benefits for applications

“…Rotating electric machines have been built using HTS in the field winding only (partially superconducting machines) [12] and in a very few cases in the armature winding as well (fully superconducting machines) [13,14]. These machines benefit from the higher air-gap field by the HTS field winding (typically producing a field of ≈3 T) and the higher current density in the stator winding [15].…”

Design and market considerations for axial flux superconducting electric machine design

“…The discovery of high temperature superconducting (HTS) materials in 1987 renewed enthusiasm for applied superconductivity research with the expectation that these materials could be exploited at 77 K, the boiling point of liquid nitrogen. Since then, a number of projects around the world have demonstrated the technical feasibility of HTS machines in various forms, including 5 MW and 36.5 MW motors for ship propulsion [6,7] by American Superconductor (now AMSC); a 380 kW motor [8], which was later developed into a 4 MW project machine [9], by Siemens; a 1.7 MW hydroelectric power generator by Converteam [10]; different HTS induction/synchronous motors at Kyoto University [11,12]; a 30 kW motor for an electric passenger car by Sumitomo Electric [13]; a 1 MW class synchronous motor for industry by KERI and Doosan Heavy Industries [14]; a 1 MW class podded ship propulsion motor by Kawasaki Heavy Industries [15]; and a sub-megawatt class propulsion system by Kitano Seiki [16].…”