Detection of temperature rise in Bi2223/Ag tape by time–frequency visualization of AE signals

This paper presents the electric insulated type detection method of the temperature rise in the Bi2223/Ag tape using the time–frequency visualization of AE signals based on the wavelet transform. At the high operation temperature, the specific heat and the normal zone propagation velocity of the Bi2223/Ag tape are high and low, respectively, and therefore the local and excessive temperature rise is easy to generate in the superconducting-to-normal transition. As a result, the Bi2223/Ag tape is degraded or burned. In the proposed method, AE signals accompanying with the temperature rise are measured by an AE sensor, and furthermore AE signals are precisely and visually measured and estimated by the time–frequency visualization using the wavelet transform. Experimental results show the feasibility of the proposed method as the detection method of the temperature rise in the Bi2223/Ag tape.