Performance Comparison of Superconducting Machines With Induction Motors

The demand for high power density electrical machines grows in aircraft and ships for their propulsion systems. Superconducting machines can be an attractive alternative for these applications. In this context, the present work presents a study comparing a superconducting motor with a squirrel-cage induction motor operating at room and cryogenic temperatures. The superconducting electric machine uses 2G tapes stacked on the rotor. The study is based on experiments with bench prototypes of conventional induction motors and superconducting motors having equal dimensions. The rotor is composed of three superconducting tape rows, which are stacked in a spiral shape around a soft ferromagnetic core. The operating principle of this machine considers the interaction of the rotating field produced by the stator with the magnetic field trapped in the superconducting tapes stacked in the rotor. A commercial 0.5-hp squirrel-cage induction motor was adapted for the tests in different circumstances for operation in an extensive temperature range. The induction machine was tested at liquid nitrogen temperature and room temperature. The results of all prototypes were compared. The authors observed that, up to 80% of the rated load, the superconducting machine works in a synchronous regime, and for higher torque's levels, it is asynchronous. Besides, it increased the torque 1.24 times and 2.43 times for the induction motor operating at room temperature and 77 K, respectively. The results showed that this superconducting machine has the potential for high power density applications.