An experimental method for total AC loss measurement of high<i>T</i>_csuperconductors

Abstract

The authors have developed a new electromagnetic method to measure the total AC loss in high Tc superconductors carrying AC transport current in an AC transverse magnetic field with arbitrary orientation. While simultaneously applying an AC transverse magnetic field and AC transport current, we measure the magnetization loss using a linked pick-up coil (LPC), and the transport loss using voltage taps with a spiral loop. Then we calculate the two to obtain the total AC loss. The LPC can be calibrated both theoretically and experimentally. One advantage of the LPC is that the error due to the variation in field orientation is negligible even if the sample superconducting tape is wide like a typical coated conductor. A precise non-inductive shunt resistor is used as the phase reference for both the magnetization loss and transport loss measurements. By combining an internal compensation coil and a non-inductive shunt resistor, we can reduce the error in the measured loss, which comes from the inductive component of the output voltage of the LPC and a phase error, to a sufficiently low level. No mechanically tunable compensation coil is required to reduce the inductive component in either the LPC output voltage or the tap voltage. An experimental system was incorporated to measure the total AC loss, and the measured total AC loss is compared with theoretical values.