Fabrication and characteristics of tapes and test magnets made from Ag-Clad Bi-2223 superconductors

Pb_0.4Bi_1.8Sr₂Ca_2.2Cu₃O_x (Bi-2223) precursor powder was prepared by a solid-state reaction of carbonates and oxides of lead, bismuth, strontium, calcium, and copper, and the powder was then used to fabricate silver-clad tapes by the powder-in-tube technique. Transport critical current density (J_c) values>4×10⁴ A/cm² at 77K and 2×10⁵ A/cm² at 4.2 and 27K have been achieved in short tape samples. Long lengths of tape were tested by winding them into pancake coils. Recently, we fabricated a test magnet by stacking ten pancake coils, each containing three 16m lengths of rolled tape, and tested it at 4.2, 27 and 77K. A maximum generated field of 2.6 T was measured in zero applied field at 4.2K and the test magnet generated significant self-field in background fields up to 20 T. The results are discussed in this paper.     

空调表冷器性能微机测试系统设计与软件开发

介绍了一套用于空调表冷器性能测试的试验装置及配套软件，重点叙述了系统的总体构成、程序的设计思想以及数据采样和处理等功能模块。微机测试技术以及配套软件的使用大大减少了测试人员的工作量，并在一定程度上提高了测试的精度。     

浅析SRT-Ⅳ裂解炉炉管弯曲及断裂原因

主要分析计算了裂解炉炉管受力情况，进而得出结论：裂解炉自身结构的相互约束力和炉管渗碳是导致炉管弯曲、断裂的主要原因，并提出了相应的解决措施。     

Flow regimes,hold–up and pressure drop for two phase flowin helical coils

Experimental results on flow pattern, hold–up and pressure drop are presented for cocurrent upward and downward air water flow in helical coils. A tube of 0.01 m internal diameter was used and the ratio of coil to tube diameter was varied from 11 to 156.5. Water flow rate was varied from 4.9 × 10-⁶ m³/s to 92 × 10-⁶ m³/s while the range of gas flow rate covered was 83 × 10-⁶ m³/s to 610 × 10-⁶ m³/s. A new mechanistic approach is proposed to correlate pressure drop data in coils. The proposed model retains the identity of each phase and separately accounts for the effects of curvature and tube inclination resulting from the torsion of the tube. This makes it possible to use a single model to predict pressure drop for both upward and downward two–phase flow in coiled tubes. Required correlations for hold–up, interfacial friction factor and friction factors for individual phases are provided.     

The Effects of Power Law Fluid Rheology on Coil Heat Transfer for Agitated Vessel in the Transitional Flow Regime

A CFD model of heat transfer from power‐law fluids to helical cooling coils in the transitional flow regime of a baffled tank mixed with a pitched blade turbine was developed with Fluent^TM. The model captured local temperature and velocity gradients. Simulations were run, varying Re, Pr, K and n. The results indicate that a Sieder‐Tate type correlation, with the exponent on and the coefficient in front of the Reynolds number being a function of n, is recommended for estimating ho. Also, a new two coil bank design was found to be more efficient when 450 < Re < 650.     

高性能PCB空心线圈电流互感器用于矿区电力系统的研究

高性能PCB空心线圈电流互感器为大截面结构,而理想空心线圈电流互感器要求为小截面结构。文章通过详细的理论分析和推导,解除了对截面大小的这一限制,得出大截面、高精度的PCB空心线圈电流互感器具有和理想空心线圈电流互感器相同测量原理的结论,为PCB空心线圈电流互感器的优化设计和在矿区电力系统中的应用提供了理论基础。实验研究结果表明,高性能PCB空心线圈电流互感器具有良好的测量精度、参数一致性、优异的工频暂态性能和抗电磁干扰能力,适应矿区的电力环境和电力系统进一步数字化的发展潮流。     

电磁流量计三值方波励磁信号的控制

电磁流量计是一种根据法拉第电磁感应定律来测量管内导电介质体积流量的感应式仪表。本文在分析电磁流量计的励磁信号种类和特点的基础上,选择了低频三值矩形方波作为电磁流量计的励磁信号,设计了电磁流量计的励磁线圈,并分析了线圈的物理和几何参数,在此基础上设计励磁系统硬件电路,包括电源、固态继电器、控制器Labjack的选型和控制方法等。最后设计了低频三值方波的控制程序,为电磁流量计提供了一种性能良好的励磁控制方案。     

基于数字信号处理器与复杂可编程逻辑器件的三相电流源型超导储能不间断电源及其控制策略

该文介绍了一种基于DSP与CPLD的三相电流源型SMES-UPS装置,该装置在电网正常时可以用作超导纵场线圈(TFSC)的励磁电源,而在电网故障时又可以用作低温和真空系统的UPS电源。在电网正常时,通过对变流器交流侧有功、无功电流的控制不但可以保证超导线圈上电流按照设定速度上升到稳态值,而且可以保证变流器网侧的单位功率因素运行和低谐波污染;在电网故障时,通过分析负载电压和电流之间的定量关系,提出了基于负载电压反馈的交流侧电流实时控制策略,不但可以保证负载电压的幅值和频率稳定,还可以电压相位不随负载性质的变化而变化。文中还介绍了基于DSP与CPLD的SMES-UPS控制系统,该控制系统结构简单、可编程程度高。1 kVA的SMES-UPS样机实验结果表明文中所述的控制算法及其控制系统能够很好地实现SMES-UPS兼作EAST纵场励磁电源和低温、真空系统UPS电源的双重功能。     

Analysis of armature reaction and winding inductances of permanent magnet brushless DC motor with deep slot concentrated coils

Based on the configuration of deep slot concentrated coils, an analytical model is developed for predicting the armature reaction field produced by the 3-phase stator windings of permanent magnet brushless DC motors with concentrated coils by using the image method and the analytical functions of the armature reaction and winding inductances are proposed accounting for the influence of stator slotting. This approach is different from the method of equivalent distributed current sheet and more suitable for electric machines, which have concentrated coils and deeper slots. Under different control mode, the different analytical functions are presented. This will be helpful when further analyzing the performance of the motor. The results agree with the experiment very well. __________ Translated from Proceedings of the Chinese Society for Electrical Engineering, 2005, 25(12): 127–132 (in Chinese)     

多参数可控的电磁生物效应综合实验装置

介绍了一种研究电磁生物效应的实验装置,采用半导体作为制冷器件,并设计了可调的电场和磁场装置和温度控制系统,可以完全通过电脑中的软件界面进行操控和测量,以探求最佳的电磁控制参数来防止生物细胞中冰晶形成以保护低温下组织细胞的存活。