Many kinds of high temperature superconductor （HTS） power machines such as HTS cable, HTS fault current limitcr and HTS magnet are cooled by liquid nitrogen. The level of liquid nitrogen should be monitored and cont...Many kinds of high temperature superconductor （HTS） power machines such as HTS cable, HTS fault current limitcr and HTS magnet are cooled by liquid nitrogen. The level of liquid nitrogen should be monitored and controlled to ensure the thermal stability and the dielectric strength as well. To measure the level, capacitance method and differential pressure method are usually used. However, each method has installation difficulties and measurement errors for unsteady state operation with varying system pressure. A new liquid level meter using a 2G HTS conductor is described, which has similar structure with the liquid helium level meter with NbTi filament. The level meter is fabricated with a parallel connected heater, which helps the separation of the superconducting region and normal region, considering the critical temperature, large heat capacity of conductor and cooling characteristics. The level of liquid nitrogen can be obtained from the measured voltage signal along the 2G HTS conductor. Design, fabrication and test results of the new liquid nitrogen level meter are presented.展开更多
Research and development of high-temperature superconducting(HTS)apparatus are ongoing in the world with the great progress on the HTS tapes in recent years.The most attractive applications require the HTS tapes to pe...Research and development of high-temperature superconducting(HTS)apparatus are ongoing in the world with the great progress on the HTS tapes in recent years.The most attractive applications require the HTS tapes to perform well upon the application of an alternative current(AC)and/or an AC magnetic field.The electromagnetic properties of the HTS tapes including anisotropy,uniformity,alternative current(AC losses)and stability as well as mechanical characteristics are important fundamental parameters for these applications.This paper summarizes and focuses on several typical measurement principles and methods as well as apparatuses of those characteristic parameters except for their stability developed in past several years in China.展开更多
We present a new calorimetric method for measuring alternative current(AC)losses of high-temperature superconducting(HTS)tapes by optical fiber Bragg grating(FBG),which is particularly well suited for the AC loss meas...We present a new calorimetric method for measuring alternative current(AC)losses of high-temperature superconducting(HTS)tapes by optical fiber Bragg grating(FBG),which is particularly well suited for the AC loss measurement of Re BCO wires,so-called the second generation(2G)HTS wires.Compared with conventional calorimetric methods,the suggested method is both free of electromagnetic disturbance,magnetic field,and fast as well as simple.Self-field AC losses are measured by the optical FBG method and the conventional lock-in-amplifier(LIA)technique,respectively.The results show that the measured AC loss is in good agreement with those measured by the electric method,thus the presented calorimetric method would be available for measuring the AC loss of 2G wire and is expected to be generalized for the measurement of AC loss or thermal performances of HTS bulk.展开更多
基金Project supported by the Second Stage of Brain Korea 21 Projects
文摘Many kinds of high temperature superconductor （HTS） power machines such as HTS cable, HTS fault current limitcr and HTS magnet are cooled by liquid nitrogen. The level of liquid nitrogen should be monitored and controlled to ensure the thermal stability and the dielectric strength as well. To measure the level, capacitance method and differential pressure method are usually used. However, each method has installation difficulties and measurement errors for unsteady state operation with varying system pressure. A new liquid level meter using a 2G HTS conductor is described, which has similar structure with the liquid helium level meter with NbTi filament. The level meter is fabricated with a parallel connected heater, which helps the separation of the superconducting region and normal region, considering the critical temperature, large heat capacity of conductor and cooling characteristics. The level of liquid nitrogen can be obtained from the measured voltage signal along the 2G HTS conductor. Design, fabrication and test results of the new liquid nitrogen level meter are presented.
基金supported by Beijing Education Commissions(Grant No.GJ2013009)the National Natural Science Foundation of China(Grant No.51077051)
文摘Research and development of high-temperature superconducting(HTS)apparatus are ongoing in the world with the great progress on the HTS tapes in recent years.The most attractive applications require the HTS tapes to perform well upon the application of an alternative current(AC)and/or an AC magnetic field.The electromagnetic properties of the HTS tapes including anisotropy,uniformity,alternative current(AC losses)and stability as well as mechanical characteristics are important fundamental parameters for these applications.This paper summarizes and focuses on several typical measurement principles and methods as well as apparatuses of those characteristic parameters except for their stability developed in past several years in China.
基金supported by the National Natural Science Foundation of China(Grant No.51477053)the Beijing Education Commissions(Grant No.GJ2013009)
文摘We present a new calorimetric method for measuring alternative current(AC)losses of high-temperature superconducting(HTS)tapes by optical fiber Bragg grating(FBG),which is particularly well suited for the AC loss measurement of Re BCO wires,so-called the second generation(2G)HTS wires.Compared with conventional calorimetric methods,the suggested method is both free of electromagnetic disturbance,magnetic field,and fast as well as simple.Self-field AC losses are measured by the optical FBG method and the conventional lock-in-amplifier(LIA)technique,respectively.The results show that the measured AC loss is in good agreement with those measured by the electric method,thus the presented calorimetric method would be available for measuring the AC loss of 2G wire and is expected to be generalized for the measurement of AC loss or thermal performances of HTS bulk.
