Investigation on low-temperature characteristics of FBG sensors and the technology to enhance sensitivity
The mode of FBG's temperature-sensing is analyzed to and the low temperature performance of FBG is experimental study. Three package technologies can be used for enhancing the sensitivity of FBG under low temperature; the technologies include capillary steel tube package, metallized package and organic polymer package. The results show that the temperature sensitivity of bare FBG under low temperature is 0.00998 nm /°C, the temperature sensitivity of FBG with capillary steel tube package, metallized package and organic polymer package are 0.0213 nm /°C, 0.0283 nm /°C and 0.1376 nm /°C separately, which are 2.02, 3.30, 10.23 times compared with the bare fiber. The temperature sensitivity of FBG sensor under low temperature could be increased effectively by using package technology.
High-sensitivity Fiber Bragg Grating Temperature Sensorwith Polymer Jacket
Temperature sensor is studied using a fiber Bragg grating fixed on polymer substrate.The wavelengths of reflected light from fiber Bragg gratings are measured in the temperature range from 2CTC to 100□.By driving effect of the polymer substrate, the temperature sensitivity was 83.07×10-6/□, that is 12.3 times as that of a bare fiber grating.
Novel rotating characteristics of a squirrel-cage-type HTS induction/synchronous motor
This paper describes the rotating characteristics of a high-Tc superconducting induction/synchronous motor, which possesses both asynchronous and synchronous torques even though its structure is exactly the same as the squirrel-cage-type induction motor. Two kinds of Bi-2223/Ag multifilamentary tapes were utilized for the secondary windings. A commercialized motor (1.5 kW) was subjected to this study. A conventional (normal conducting) stator (three-phase, four-pole) was directly utilized, and only the squirrel-cage windings were replaced with the superconducting tapes. The tests were performed after the fabricated motor was immersed in liquid nitrogen. The operating temperature was also varied by pumping out the liquid nitrogen. It is shown that the motor is successfully synchronized for the temperature range from 65 to 77 K. Detailed discussions for such novel rotating characteristics are reported based on the electrical equivalent circuit.