Experimental and Analytical Studies on Variable Speed Control of High-Temperature Superconducting Induction/Synchronous Motor

We try to realize variable speed control technology of superconducting drive motors in order to apply such motors to transportation equipment, i.e., trains, buses, automobiles, etc. Our target motor is the so-called high-temperature superconducting induction/synchronous motor (HTS-ISM). Based on experiments and analyses, we have already shown that the HTS-ISM has prominent performance such as highly efficient synchronous rotation in the steady state. On the other hand, a detailed study for the variable speed control is not carried out yet. In this paper, we first perform a starting test of a 20-kW-class HTS-ISM and then succeed in accelerating the HTS-ISM from 0 to 1500 r/min just for 0.4 s. Second, we succeed in controlling the HTS-ISM for variable speed under the drive mode called standard JC08. Next, we assume that there should be three kinds of rotational modes upon the acceleration of the HTS-ISM, which are expressed by the use of a transfer function. It is shown that the analytical results agree well with the phenomenon in the experiment we conducted. These results indicate that it is possible to accelerate the HTS-ISM under not only the slip mode but also the highly efficient synchronous mode.