Measurement System for Induced Currents in Superconducting Air-Core Rotors for Induction Motors

We are conducting research and development of an all-superconducting induction motor with lightweight. A lightweight induction motor can be realized by making the rotor without an iron core. To evaluate the characteristics of the induction motor without an iron core and to design an optimal induction motor, it is necessary to quantitatively clarify the characteristics of the current flowing in the superconducting rotor with an air core. In this study, an experimental apparatus was developed to measure the induced current flowing in a rotor exposed to a rotating magnetic field using a pickup coil. In the experiment, a squirrel-cage rotor sample made of YBCO tape 81 mm in diameter and 170 mm in length was placed in a space 120 mm in diameter, and a rotating magnetic field was applied. The temperature of the rotor sample is liquid nitrogen temperature. The rotor sample consisted of six rotor bars and end rings. The rotor bars consisted of one wire with a critical current of 110 A. The magnetic moment of the rotor was measured with three pickup coils, and then the induced current in the rotor was evaluated.