对电机绕组圆形接线图极相组排列次序的质疑和建议

在教学中使学生掌握定子绕组的基本结构、连接方法及展开图的绘制,有利于学生高质量、高效率地掌握知识和技能。

《电机与变压器》中圆形接线图极相组排列次序的质疑和建议

教学中掌握定子绕组的基本结构、连接方法及展开图的绘制,有利于学生高质量、高效率地掌握知识、技能。

两级48槽定子线圈极相组连接错误对电机影响的实例

1979年初我厂为唐山钢铁公司大修一台上海电机厂1974年出品的 JKZ 1250 2型.1250kW 异步电动机。解体测绘和记录有关数据为:定子槽数 Q_J=48.

金相组动态管理考核办法及实施细则

金相组动态管理考核的主要内容有:工作业绩、工作表现、出勤率。1.工作业绩:占总考核分50%。(1)高倍试样:试样制备3分+检验项目1分/项(JK图评级2分);(2)断口试样:2分/件,现场高倍磨制试样的分值由参加人员评分;(3)综合报告:5分/份,特殊报告:10分/份;

单神经元自适应控制PSD在再热汽温控制中的应用

提出了一种新型具有负荷前馈—串级反馈的再热蒸汽温度控制系统。其外环 (主环 )采用单神经元自适应PSD控制器 ,其内环 (副环 )采用双自由度PID控制器。并使用Bai ley公司的CLC 0 4型单回路数字调节器进行设计、组态和实现。仿真研究和现场运行表明该系统具有良好的控制效果。

Phase transformation in titanium alloys:A review

Due to a series of exceptional properties,titanium and titanium alloys have received extensive attention in recent years.Different from other alloy systems,there are two allotropes and a sequence of metastable phases in titanium alloys.By summarizing the recent investigations,the phase transformation processes corresponding to the common phases and also some less reported phases are reviewed.For the phase transformation only involvingαandβphases,it can be divided intoβ→αtransformation and a reverse transformation.The former one has been demonstrated from the orientation relationship betweenαandβphases and the regulation ofαmorphology.For the latter transformation,the role of the stress has been discussed.In terms of the metastable phases,the mechanisms of phase formation and their effects on microstructure and mechanical properties have been discussed.Finally,some suggestions about the development of titanium alloys have been proposed.

Effect of forging on the microstructure and texture of a high Nb containing γ-TiAl alloy

The effect of forging on the microstructure and texture evolution of a high Nb containing Ti-45Al-7Nb-0.3W(at.%)alloy was investigated by X-ray diffractometer(XRD),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).The results show that the as-cast alloy is mainly composed of α_(2)/γ lamellar colonies with a mean size of 70μm,but the hot-forged pancake displays a near duplex microstructure(DP).Kinking and bending of lamellar colonies,deformation twinning and dynamic recrystallization(DRX)occur during hot forging.Meanwhile,dense dislocations in theβphase after forging suggest that the high-temperature β phase with a disordered structure is favorable for improving the hot-workability of the alloy.Unlike the common TiAl casting texture,the solidification process of the investigated as-cast alloy with high Nb content is completely via the β phase region,resulting in the formation of a<110>γ fiber texture where the<110>γ aligns parallel to the heat-flow direction.In comparison,the relatively strong<001>and weak<302>texture components in the as-forged alloy are attributed to the deformation twinning.After annealing,static recrystallization occurs at the twin boundary and intersections,which weakens the deformation texture.

结合一体化教学谈交流绕组节距的简易确定

交流电机的绕组发生故障时,经常需要重新绕制线圈进行更换,而绕组节距的确定是绕制线圈的关键。结合理论知识、实践经验以及绕组工艺,给出三相交流电机单层绕组节距的简易确定方法。

Effect of mole ratio of Y to Zn on phase constituent of Mg-Zn-Zr-Y alloys

The phase constituent evolution of Mg-Zn-Y-Zr alloys with the mole ratio of Y to Zn both in the as-cast and as-annealed states at the Mg-rich corner was investigated by XRD and SEM/EDS analysis and was further explained from the ternary phase diagram calculation. The results show that the formation of the secondary phases in Mg-Zn-Y-Zr alloys firmly depends on the mole ratio of Y to Zn, and X （Mg 12 YZn）-phase, W （Mg 3 Y 2 Zn 3 ）-phase and I （Mg 3 YZn 6 ）-phase come out in sequence as the ratio of Y to Zn decreases. The mole ratios of Y to Zn with the corresponding phase constituent are suggested quantitatively as follows： the phase constituent is α-Mg ＋ I when the mole ratio of Y to Zn is about 0.164; α-Mg ＋ I ＋W when the mole ratio of Y to Zn is in the range of 0.164 0.33;α-Mg ＋W when the mole ratio of Y to Zn is about 0.33; α-Mg ＋W＋X when the mole ratio of Y to Zn is in the range of 0.33 1.32; and α-Mg ＋X when the mole ratio of Y to Zn is about 1.32. The results also offer a guideline for alloy selection and alloy design in Mg-Zn-Y-Zr system.

Technological mineralogy and environmental activity of zinc leaching residue from zinc hydrometallurgical process

Chemical, physical, structural and morphological properties of zinc leaching residue were examined by the combination of various detection means such as AAS, XRF, XRD, M？ssbauer spectrometry, SEM-EDS, TG-DSC, XPS and FTIR. The toxicity characteristic leaching procedure （TCLP） was used to investigate the environmental activity of zinc leaching residue for a short contact time. The phase composition analysis indicated that the zinc leaching residue mainly consists of super refined flocculent particles including zinc ferrite, sulfate and silicate. The physical structural analysis showed that it has a thermal instability and strong water absorption properties. The results of TCLP indicated that the amounts of Zn and Cd in the leaching solution exceed 40 and 90 times of limit, respectively, which demonstrate that this residue is unstable in weak acidic environment for a short contact time.

气隙不均匀对异步电动机电磁噪声的影响

异步电动机转子偏心会引起一系列低次数径向力波,并使噪声辐射增加。转子偏心实际上不可能完全消除,本文采用适当的定子绕组并联支路,将每一对极两端以均压线连接在一起,由于径向相对的极相组电抗不同在均压线上引起均衡电流,从而削弱了偏心的有害影响。实验结果表明,该方法能够有效降低因偏心引起电磁噪声。

Microstructure evolution of Zn-8Cu-0.3Ti alloy during hot deformation

The hot deformation behavior of homogenized zinc alloy was investigated through uniaxial compression test on a Gleeble-1500 thermal-mechanical simulator within a temperature range of 230-380°C and a strain rate range of 0.01-10 s -1 ,the corresponding flow curves and their characters were determined and analyzed,and microstructures were studied by optical,SEM and TEM microscopy.The results indicated that the microstructure evolution of zinc alloy during hot deformation involves the spheroidization of the phase of TiZn15,coarsening of the precipitated phase and dynamic recrystallization（DRX）of the phase of matrix,leading to the formation of the polyphase（η＋ε＋TiZn15）structure.The spheroidization of the phase of TiZn15 during hot deformation was beneficial to the particle nucleation stimulated and then promoted to DRX of matrix.The dynamic recrystallization grain size of the matrix phase decreased firstly and then increased with elevating the temperature,and the degree of DRX became more complete when the strain rate and strain became larger.Hot deformation accelerated the diffusion of Cu atom,which resulted in the coarsening of the precipitated phase.Thus,the microstructure was refined owing to the pinning effect of the precipitated phase.

Morphology and crystallography of β precipitate phase in Mg-Gd-Y-Nd-Zr alloy

Morphology and crystal structure of β precipitate phase in Mg-7Gd-5Y-1Nd-0.5Zr (mass fraction, %) alloy were characterized by optical microscopy, scanning electron microscopy and transmission electron microscopy. Compositions were determined for β phase using thin foil energy dispersive spectroscopy. Precipitation at 400 ℃ involves formation of platelet and block-shaped β phase. The orientation relationship is and between β precipitate phase and α-Mg matrix with habit planes parallel to , and a composition of Mg5(Y0.4Gd0.4Nd0.2) is suggested for the β phase in Mg-7Gd-5Y-1Nd-0.5Zr alloy.

Effects of on-line solution and off-line heat treatment on microstructure and hardness of die-cast AZ91D alloy

The effects of on-line solution, off-line solution and aging heat treatment on the microstructure and hardness of the die-cast AZ91D alloys were investigated. Brinell hardness of die-cast AZ91D alloy increases through on-line solution and off-line aging treatment but decreases after off-line solution treatment. By X-ray diffractometry, optical microscopy, differential thermal analysis, scanning electron microscopy and X-ray energy dispersive spectroscopy, it is found that the microstructures of the die-cast AZ91D magnesium alloy before and after on-line solution and off-line aging are similar, consisting of α-Mg and β-Al12Mg17. The precipitation of Al element is prevented by on-line solution so that the effect of solid solution strengthening is enhanced. The β-Al12Mg17 phases precipitate from supersaturated Mg solid solution after off-line aging treatment, and lead to microstructure refinement of AZ91D alloy, so the effect of precipitation hardening is enhanced. The β-Al12Mg17 phases dissolve in the substructure after off-line solution treatment, which leads to that the grain boundary strengthening phase is reduced significantly and the hardness of die cast AZ91D is reduced.

Microstructure and phase precipitate behavior of Inconel 740H during aging

The microstructure and phase precipitate behavior and their effects on the room temperature hardness and impact toughness of Inconel 740H aged at 750 ℃ for 10000 h were investigated by SEM, TEM and mechanical analysis. The as-received alloy shows a low hardness value of HB 168 and a highest toughness value of 96 J. After an aging treatment at 800 ℃ for 16 h and cooled in air （standard heat-treated condition）, fine γ′ phase particles precipitate within the grains and small carbide particles are located at the grain boundaries. The hardness increases to HB 304 and the impact toughness decreases to 15 J after standard heat treatment. A maximum hardness value of HB 331 is achieved for the alloy aged at 750 ℃ for 300 h. With increasing the aging time from 300 to 10000 h, a decrease of the hardness and toughness is observed along with an enhanced quantity of M23C6 particles and the coarsening of γ′ phase.

Effect of pre-deformation on microstructures and mechanical properties of high purity Al-Cu-Mg alloy

The effects of pre-deformation following solution treatment on the microstructure and mechanical properties of aged high purity Al-Cu-Mg alloy were studied by tensile test, micro-hardness measurements, transmission electron microscopy and scanning electron microscopy. The micro-hardness measurements indicate that compared with un-deformed samples, the peak hardness is increased and the time to reach peak hardness is reduced with increasing pre-strain. Additionally, a double-peak hardness evolution behavior of cold-rolled （CR） samples was observed during aging. The results of TEM observation show that the number density of S′（Al2CuMg） phase is increased and the size is decreased in CR alloy with increase of pre-strain. The peak hardness and peak strength of the CR alloy are increased because of quantity increasing and refinement of S′ phase and high density dislocation.

Microstructure of cast γ-TiAl based alloy solidified from β phase region

The microstructures and phase transformation of Ti-43Al-4Nb alloy in as-cast and heat-treated states were investigated by using optical microscopy, scanning and transmission electron microscopy as well as differential scanning calorimetry. The results show that a fine microstructure of the as-cast alloy can be obtained by solidifying through the β phase. γ grains can nucleate directly from the β phase. The coexistence of β phase and γ phase along primary α grain boundaries contributes to the decrease in the grain size of the as-cast alloy. The phase transformation sequence during solidification of the Ti-43Al-4Nb alloy is suggested as L→L＋β→β→α＋β→α＋βr→α＋γ＋βr→lamellae（α2＋γ）＋γ＋βr. The microstructure of the alloy after heat treatment at 1 250 ℃ for 16 h exhibits a certain coarsening compared with that of the as-cast state. The remnant β phase can be removed by the heat treatment process due to the diffusion of Nb and the non-equilibrium state of β phase.

Microstructure and mechanical properties of high strength Al-Zn-Mg-Cu alloys used for oil drill pipes

Three Al?Zn?Mg?Cu alloys used for oil drill pipes (Alloy A: Al?6.9Zn?2.3Mg?1.7Cu?0.3Mn?0.17Cr; Alloy B: Al?8.0Zn?2.3Mg?2.6Cu?0.2Zr, Alloy C: Al?8.0Zn?2.3Mg?1.8Cu?0.18Zr) were studied by hardness tests, tensile tests and transmission electron microscopy (TEM). The results show that the ultimate tensile strength, yield strength and elongation for Alloys A, B and C are 736 MPa, 695.5 MPa and 7%; 711 MPa, 674 MPa and 12.5%; 740.5 MPa, 707.5 MPa and 13%, respectively after solid solution treatment ((450 °C, 2 h)+(470 °C, 1 h)) followed by aging at 120 °C for 12 h. The dominant strengthening phases in Alloy A are GPII zone andη′ phase, the main precipitate in Alloy B isη′ phase, and the main precipitates in Alloy C are GPI zone, GPII zone andη′ phase, which are the reason for better comprehensive properties of Alloy C. The increase of zinc content leads to the improvement of the strength. The increase of copper content improves the elongation but slightly decreases the strength. Large second-phase particles formed by the increase in the manganese content induce a decrease in the elongation of alloys.