Study on AC Loss Characteristics of 3-Phase HTS Coils With Iron Core and Its Reduction

Abstract

Study on ac loss characteristics of HTS coils with an iron core to simulate an armature winding of ac rotational machine and a method to reduce ac losses in HTS coils combined with the iron core in 3-phase condition are reported in this paper. In this study, the 3-phase test model which combines 6 HTS coils wound by YBCO tapes and the iron core used for an armature of conventional induction motor is fabricated for the ac loss measurement. It is shown that the measured ac losses in the 3-phase condition coincides with the sum of the ac loss of each phase measured in the 1-phase condition. The effectiveness to suppress the perpendicular magnetic field applied to the tape in the coil by use of magnetic materials around the coil winding on the ac loss reduction in the 3-phase condition is investigated. The measured ac loss with placing the magnetic material around the coil winding in the slot of the iron core remarkably decreases. The results of the numerical magnetic field analysis confirmes that the perpendicular magnetic field significantly decreases by arranging the magnetic material and supportes the validity of the measurement results. The results obtained in this study demonstrates that the effectiveness to modify the magnetic field distribution by use of the magnetic material around the coil winding on the ac loss reduction in 3-phase HTS coil combined with the iron core.