6 kV电动机定子绝缘诊断和剩余寿命预测

介绍了6kv电机定子绝缘老化过程。讨论了绝缘诊断的项目及具体进行的测试。介绍了某公司1台已运行9a的6kV电机诊断测试数据及评定结果。由此说明了高压电机定子绝缘老化诊断和剩余寿命预测的必要性。     

利用低电压电流烘干大电机

1995年，我们在越南建江省安装、调试8．8t机立窑生产线过程中，发现两台380kW／6000U高压电机和一台75kW／380V二破电机受潮，绝缘较低，其中用于2500V绝缘表测得两台6000高压电机定子绕组对地绝缘电阻小于100MΩ。用500V绝缘表测得75kw／380V电机定子绕组对地绝缘电阻为0。据     

大型高压电动机主绝缘升级的探讨

大型高压电动机绝缘的可靠性是电机寿命长短及可靠性的重要标志。电机定子绕组是电机的心脏，其寿命直接影响电机的安全运行。我公司有高压电动机28台，其中同步电动机12台，异步电动机16台，均采用B级绝缘，除1台3#铜泵电动机为全封闭空冷电动机，绝缘良好外，其余高压电动机皆为开启式电动机，每逢阴南季节，定子绕组对地绝缘小于6MΩ，甚至降为0，严重影响生产。     

同步电动机轴承的电蚀和维护

由于同步电动机运转中产生轴电压,如果轴承底座的对地绝缘维护检查不够及时,则轴承极易被电蚀,影响其使用寿命,电机的可靠性也随之降低。通常,大中型电机的定子铁芯,多由数张扇形硅钢片拼装成一个整圆,因为所用扇形硅钢片的片数为奇数,所以电机的每个磁极所占据的扇形片接缝数和由此而形成的气隙长度不等;由于电机制造,安装,检修等原因,电机定子与转子之间的气隙长度沿整个圆周也不处处相等。这就使电机各并联磁路不完全对称,     

高压交流电机超低频耐压试验

为了克服交流工频耐压试验中气隙、裂缝放电和电机绕组产生热效应加速绝缘老化等缺陷,我国从七十年代中期开始对超低频(0.1赫)耐压试验进行研究和现场试验,取得了不少经验和有价值的数据,为超低频耐压试验取代交流工频耐压试验创造了条件。一、超低频耐压试验的特点对电机绝缘进行交流耐压试验,从电压分布看,既要使电机绝缘的耐压试验条件力求接近于实际运行条件,又要尽可能减小耐压试验对绝缘的破坏性。国内外大量试验表     

静止式进相器的使用与改造

0前言 静止式进相器是专为大中型绕线式异步电机设计制作,接于电机转子同路的无功功率就地补偿装置.异步电动机正常运行后,静止式进相器采集电机转子电流信号,经微处理器CPU处理后给可控硅晶闸管发出触发信号.由可控硅晶闸管组成的交一交变流器将工频电源变为和电机转子电流同频率的附加电势,加在电机转子回路中,改变转子电流和转子电压的相位关系,通过磁场进而改变电动机定子电流和定子电压的相位关系,减小功率因数角,提高电动机功率因数.     

自感电势引起高压电机绝缘损坏问题的探讨

1994年,我厂发生一起JR158——8,6000V,380kW高压电机定子线圈匝间绝缘损坏事故。 该电机用于φ2.2×6.5m生料磨,时间约为2年,查有关资料:定子耐压13000V,转子耐压2500V,均有合格的测试报告单。查表与测量相间绝缘和相对地绝缘电阻均可。我们把问题的重点放到高压起动柜上。     

高压容器内600KW透平电机绝缘降低报警装置的设计制作

一、概述我厂新安装的透平循环压缩机为内置式,即电动机和透平压缩机直接联接后一齐置于高压容器内,并在高压气体介质中运转。与往复式循环压缩机相比优点甚多,但对电气提出了更高的要求,特别是置于高压容器内电动机的绝缘问题。1986年3月9日,该电机在运行中,因电机定子内进氨、水和油等杂物,使定子线圈绝缘下降,发展到两相对地,造成定子线圈相间短路。虽过流保护跳闸,但定子铁芯及线圈仍被烧毁。     

静止式进相机可控硅和阻容吸收元件频繁烧坏的原因分析及解决措施

<正>我公司水泥磨绕线式电机型号YRKK900-8,额定功率3550k W,额定电压10k V,转子电压1597V,转子电流1343A,选用的静止式进相机是襄樊某公司的SPM5-1500,作为绕线式电机的就地式无功功率补偿装置,用于提高电机功率因数和效率,降低电机定子工作电流和定子绕组温升。     

高压大容量电动机定子绕阻损坏原因分析及故障点查找

在发电厂,包含发电机、变压器、高低压开关、电力电缆等各种电气设备。其中也包括大量高、低压交流电动机。电动机在启动过程中,由于电磁力的原因,定子线圈端部和引线将受到较大的电动力作用。随着电机运行年限的增长,定子线棒的绝缘材料逐渐老化,电机运行时频繁启动,对电机寿命危害更为严重。线圈端部槽口处和绕阻连接线焊接部分成为遭受电动力破坏的薄弱环节。开焊断股、温度升高.进一步恶性循环而使绝缘损坏造成对地或相间短路,使高压电机发生严重损坏事故。怎样预防电机故障,及早发现电机故障的隐患是摆在电气试验人员面前的一道难题。本文根据自己在工作中的一些体会,及现场实际事例,结合传统和现代试验方法对大容量高压电机定子绕阻故障诊断方法进行了论述和总结,对以后防止电机烧毁及损坏,保障安全运行有着极其重大的意义。     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料,介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比,介绍了中国塑料的生产情况。按通用热塑性树脂（聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂）、工程塑料（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序,对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。