Magnetization Loss Characteristics of a GdBCO Tape in kHz Frequency Band

Abstract

We have investigated the application of a high-temperature superconducting (HTS) coil to a high-power wireless power transmission system operated in the frequency region less than 10 kHz. In order to reduce the ac loss of the HTS coil, it is necessary to clarify the characteristics of magnetization loss in the HTS tape with a copper layer in the kHz frequency band. Therefore, we prepared GdBCO tapes with and without the copper layer and measured the magnetization loss of the GdBCO tape exposed to a vertical magnetic field in the kHz frequency band. We analyzed the ac losses of the GdBCO layer, the copper layer, and the other layers within the tape by a finite element method analysis. The influence of the copper layer thickness on the ac loss in each layer was investigated by a finite element method (FEM) analysis. The magnetization loss per cycle of the GdBCO tape slightly decreased with the frequency. The magnetization loss, however, can be approximately estimated by Brandt's formula with a certain accuracy when the n value of the tape is large. In the GdBCO tape with the copper layer, when the external magnetic field was large, the magnetization loss per cycle of the GdBCO layer was larger than the copper layer loss. The magnetization loss, however, decreased and the copper layer loss increased with the thickness of the copper layer. The total loss of the GdBCO tape can be reduced by placing the coppers layer near the GdBCO layer.