Development of a HTS squirrel cage induction motor with HTS rotor bars

Efficiency at full load and starting torque at starting are basic performance criteria of the induction motor. Conventionally deep bar or double cage bar have been used to increase the efficiency and starting torque of the induction motor. Effective resistance of the deep bar and double cage differs from starting to full load operation. To increase the efficiency and starting torque, HTS tapes can be used as the rotor bars. The resistance of HTS tapes develops at starting because of large starting current which exceeds the critical current of the HTS tape and it vanishes as the speed builds up. This paper presents the construction and test results of a HTS induction motor. End rings and short bars were made of HTS tapes. Stator of the conventional induction motor was used as the stator of the HTS motor. Rated capacity of the conventional motor was 0.75 kW. Performances of the HTS induction motor were compared with those of the conventional motor with same volume and specification. Test result showed that the speeds of the HTS induction motor were the same with synchronous speed up to 2.6 Nm and 1788 rpm at 9.7 Nm. It guarantees the high efficiency of the HTS motor. Starting torque of the HTS motor was more than twice of the conventional motor.