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1.
该变频装置采用三菱公司功能强大的可编程控制器(PLC),因而本变频装置结构简单、控制精度高、稳定性强、可靠性高、灵活性好,极大地改善了变频装置的功能和性能:具有实时显示设备工作状态,运行的实际参数及故障原因的功能、实现了系统的超速保护、反转保护、电机超温保护、过载过流保护等;变频装置主回路采用德国产IGBT功率器件及应用PWM控制技术,使系统实现了电气反馈制动,具有环保节能品质,电机噪声达到了人耳难于感知的频段。 相似文献
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为了减少三相异步电动机在运行过程中的损坏次数及设备故障率,降低维修费用,提高电动机运行的可靠性,设计了一种以SPMC75F2413A单片机为控制核心的电机状态监测系统.采用理论分析和实验的方法,提出了基于对称分量法的电动机保护算法,实现了监测系统的软硬件设计.研究结果表明:该系统可在线监测三相电动机的各种运行状态,如过载、堵转、三相短路、漏电等,通过无线方式与监控系统主机通信,进行保护和控制.该监测系统可广泛应用于电厂、油田、煤矿等领域. 相似文献
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《合肥工业大学学报(自然科学版)》2015,(9)
针对传统热继电器在电机运行保护时存在的灵敏度低、调整误差大、功耗大、耗材多、性能指标落后等缺陷,文章设计一种新型电机过载保护装置,该装置利用一个磁环感应线圈采集电机的某一相电流信号,同时采用线路板以干触点接入交流接触器控制线圈回路,该方式能适应多种规格的交流电机保护。另外不同于传统保护方法只检测高限,文中所设计装置还包含低限检测线路,并通过对称负载中一相电流的变化来反映电机不同的工作状态,在保障电机不被损坏的情况下充分利用电机的过载能力。 相似文献
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要想实现全厂节能降耗。首先以输煤水冲洗泵作为输煤系统节能减排的项目将水泵电机在工频运行状态改为采用变频器变频调速的方式,来降低用电量的损耗和保护电机,延长电机使用寿命的手段。 相似文献
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本文介绍湘潭钢铁公司轧钢厂线材轧机生产线上40台电机工作状态无线遥测计算机管理系统。该系统采用无线发射与接收装置将电机的工作状态转换为数字信号后送8032单片机进行检测运算处理,在CRT上显示出各台电机事故停车的起始时间,每隔8h打印出每台电机的停车时间及停车总次数等。该系统的运用,使轧机的生产水平得到提高. 相似文献
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针对轿车举窗工作中产生的热量可能烧毁举窗电机的问题,提出了一种基于软件的举窗电机热保护方法。通过分析轿车举窗永磁直流电机在三种工作状态下的温度变化原理,建立了相应的热保护算法数学模型,设计了电机工作温度的实时监测软件。在电源电压为12.5 V 和14.5 V 条件下对软件监测方法进行了实验验证,结果显示,监测温度与实测温度的误差小于5℃,表明该方法对电机温度变化的监测具有较高的准确性,可实现对轿车举窗电机的热保护。该方法在无温度传感器的电机温度保护领域具有一定的应用前景。 相似文献
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开发了一个地毯簇绒机的伺服电机状态监测系统,该监测系统建立在原有CAN总线结构基础上,设计了监测系统的硬件结构,实现了对地毯簇绒机上受控电机的状态实时监测.从系统构架和软件设计两方面阐述了监测系统的原理和实现方法.利用Delphi开发了监测软件,并进行了现场测试,实时在线监测电机运行状态,方便地毯簇绒机提花机构中伺服电机现场的安装调试以及故障检测. 相似文献
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介绍了邯钢中板厂主要电机新系统基本特征,对轧制工艺的作用做了简要的分析。实际测试表明,实际测试表明,该系统在过载保护、控制灵敏性,稳定性方面比以前明显提高,上下电机工作均衡,但加负荷后速度降较大,表明该电机特性较软。该系统投入使用后,对该厂品种钢的开发创造了良好的设备条件。 相似文献
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利用光纤温度传感器探测矿井提升电机机轴发热产生的温度信号,并将此信号转换成电信号,经系统放大、计算、比较、存储、分析电机机轴的温升情况,并对温度超标的电机机轴实时报警。根据该系统提供的数据,维修人员能够准确地了解运行电机机轴的技术状态,及时发现热轴故障,采取预防措施,避免电机机轴过热造成重大提升事故。同时,该系统还能极大地减轻作业人员的劳动强度,避免因经验不足和判断失误等因素造成的误报、漏检、热轴事故,减少了安全隐患。 相似文献
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Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness. 相似文献
12.
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly. 相似文献
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理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。 相似文献
14.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death. 相似文献
15.
Miao Maosheng 《华南师范大学学报(自然科学版)》2014,(6)
正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula- 相似文献
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Yang Weitao 《华南师范大学学报(自然科学版)》2014,46(6):137-138
We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re- 相似文献
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Bernard Kirtman 《华南师范大学学报(自然科学版)》2014,(6)
正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that 相似文献
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《上海师范大学学报(自然科学版)》2014,(5):550
<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with 相似文献
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《吉林大学学报(理学版)》2014,(5):1105
<正>"Journal of Jilin University(Science Edition)"is a comprehensive academic journal in the fields of science sponsored by Jilin University and administrated by the Ministry of Education of the Peoples Republic of China.The journal started publication in 1955.The original name at starting publication was"Journal of Natural Science of Northeast People University",which was changed into"Acta Scientiarum Naturalium Universitatis Jilinensis"in 1958 owing to the name change of the university.The present journal name has 相似文献