Calorimetric methods for measuring AC losses in HTSC tapes carrying currents
Power engineering applications of HTSC tapes are often restricted by AC losses. Both direct and indirect methods have been used to measure AC losses in short samples. This paper reports on the development of a direct calorimetric method for AC loss measurement techniques for short tapes based on measurements of slight temperature increases of the sample. This method has the advantage of measuring total losses in the HTSC sample. The test rig discussed here consists of a calorimeter and associated data collection and analysis equipment. The calorimeter uses a sensitive temperature sensor and an ohmic heater, needed for the calibration of the system, surrounded by a thermal insulator. A platinum sensor is used which works at 77 K and may be used in a magnetic field. Sensors and controlled variables are interfaced to the controlling computer via IEEE interfaces. The power loss of a sample carrying alternating current has been measured with a high accuracy using this experimental set-up. The sample is a seven-filament BSCCO-2223 tape. In addition, the effect of the frequency and amplitude of the signal has easily and quickly been analysed.