电机单相保护与温升监控

电动机烧坏的原因一般以单相运转为主,而且电机的烧坏,都归因于电机绕组的温升超过允许值。为此,我们试制了电动机的单相快速保护与温升监控保护器,成功地对电机进行全面、快速保护。单项故障发生后2秒内可切断电源;电机的温升监测误差小于2℃,达到控制温度时切断电源的动作     

三相电机缺相运行自动保护器

我国的农电事业,在毛主席的无产阶级革命路线指引下,正在迅猛发展,用电范围日益扩大。为了解决三相电机缺相运行的问题,我校师生,在教育革命实践中,试制成功了三相电机缺相运行自动保护器 农用电机中,例如灌溉水泵,经常是在无专门机手看管的情况下运行。有时由于电源部分或电机本身的保险丝烧断,造成电机缺相运行,使电机的温度不断升高,可能导致电机被烧毁,造成人民财产的损失;或因温度升高绝缘损坏而漏电,造成触电伤亡事故。三相电机缺相运行自动保护器,能在电机缺相运行时,自行迅速切断电源,防止上述事故的发生。它可用在不同型号及功率的…     

电磁液压安全闭锁停层保护装置

唐山市某水产食品有限公司因简易升降机在停层装货时突然下降 ,致使一工人跌入吊笼和夹墙之间被绞死 ,经过我所对这起死亡事故的原因进行现场检验和分析认为 ,这台简易升降机主要传动机构只靠顶端固定的一台电动葫芦起升和下降。葫芦电机采用锥形定转子 ,当正常工作时 ,电机的定子通电流产生磁性 ,使转子拉向中心位置 ,同时制动环脱离端盖进行转动。当电源中断时 ,弹簧把转子拉向原位 ,制动环即随转轴移动进行制动。根据以上情况电葫芦在上升和下降的运行过程中由于电机定子有磁性 ,不会突然失灵下掉 ,只有在电源中断时受电机压力弹簧装置制…     

厂矿企业大宗原、燃料卸车机械安全改造技术

厂矿企业卸车机械长期运行,存在设备老化、检修频繁的现象.通过对卸车机械存在安全隐患的分析,论述了机械系统的行走机构、挖掘机构、钢结构框架、皮带输送机构、操作室和电气系统的供电电源、大车行走电机回路、卷扬电机等部件的安全改造技术.     

起重机械供电电源断错相保护功能的检验

供电电源断错相保护是交流供电起重机械重要的电气安全保护措施。其中,断相保护主要是为了防止因供电电源断相时造成电机断相运行而烧坏电机,从而有效避免可能发生的起重机机构失速事故。而错相保护则主要是为了防止因供电电源相序发生变化而造成如起升高度限位器、大车和小车运行机构限位器等安全保护装置失效,同时还可以防止操作人员对机构的误操作（无错相保护时,起重机操纵控制器的功能指示方向与相应机构的实际运行方向相反）。由此可见,供电电源断错相保护功能对起重机械的安全运行具有举足轻重的作用。1断错相保护功能的实现1．1断错相保护功能的实现形式与要求供电电源断错相保护功能一般是通过设置断错相保护器（以下简称“保护器”）来实现的。保护器是一种用于监测供电电源状态并发出电气信号的开关元件,即当保护器监测到供电电源出现断相或相序错误时,立即发出电气开关信号,并促使异常供电电源分断（断开或防止接通）。对于起重机而言,当供电电源出现断相或相序错误时,要求能可靠断开各机构的动力电源。     

建筑消防负荷计算与柴油发电机容量选择

在建筑物中,作为备用电源或应急电源的柴油发电机组其容量常按照满足稳定负荷容量、满足单台最大或成组电机启动需求以及满足电机启动母线允许电压降三者最大值进行确定;对于非消防一、二级负荷不多的高层民用建筑,发电机容量一般按同时运行的消防负荷加载最大功率的电动机启动需求进行容量选择,但如何精确计算同时运行的消防负荷,常让电气设计人员比较困惑。本文将重点阐述柴油发电机容量的选择以及消防负荷精确计算的原则和方法,供读者参考。     

矿用局扇保护起动器

矿用局扇工作环境恶劣,一般又无专用的电机保护装置,因而烧坏很多。据调查,冶金矿山局扇电机年烧坏率约达30％。局扇电机烧坏的原因有绝缘击穿、断相(单相)或过载运转(因局扇叶轮卡住或电机轴承损坏而造成)引起绝缘老化,其中以断相烧坏的比例最大。电机由于熔断器(保险丝)一相熔断、电源一相断线、电机绕组引出线和接线柱一相联结松脱、接触器或开关一相接头损坏等,都可能造成断相运转。为此,在调查学习一些兄弟单位的先进     

起重机电气系统中的安全保护措施

(1)过流保护。在电机定子或电枢回路中串入过流继电器,当电机内流过超过允许值的电流时,过流继电器动作,使电机断电停止工作。 (2)短路保护。常用熔断器或自动空气开关作短路保护,熔断器有时熔断后会造成单相运行,应避免。 (3)过热和断相保护。在交流电机定子回路中串入热继电器,保护电机不过热。 (4)失压和零位保护。失压保护能在系统失电时待系统恢复供电后,机构自动恢复运行。零位保护能避免接通电源后,由于控制器手柄不处于零位造成的机构自动运行。 (5)紧急开关。在紧急情况下,司机操作     

自动扶梯曳引机由静态元件供电的拖动线路及PLC控制

文章分析了GBI6899—2011《自动扶梯和自动人行道的制造与安装安全规范》中曳引电机由静态元件供电的要求,讨论了使用两个和一个电源接触器切断曳引机供电的线路。并优先使用一种两个电源接触器切断供电的线路,设计了该线路的一种PLC控制电路,讨论了其起动和停止的控制过程。并给出了PLC控制梯形图程序的结构图。     

低噪声调速式电机振动给料机

调速式电机振动给料机系机械工业部济南铸造锻压机械研究所研制的一种以振动电机为激振源的新型给料设备。 它与电磁振动给料机相比,具有噪声低(低于75分贝(A)〕、功率因数高、结构简单、调节维修方便、给料性能受电源电压波动影响小等优点。此外,该机可以无级调速(调速比宽为1:10),给料均匀,给料精度较高。可满足各行业对配称精度的要求。 这种低噪声调速式电机振动给料机应用广泛,前不久已被有关部门通过技术鉴定,机械工业部济南铸造锻压机械研究所已技术转让,由济南振动机械厂生产。低噪声调速式电机振动给料机$济南振动机械厂@李曾琨…     

行星传动起升机构飞车原因分析

建立行星传动起升机构电动机飞车的模型,计算电动机失电后各瞬间重物的速度、加速度,电动机的转速,从而分析事故的原因。     

“自由落体”游乐设备直流电机故障分析

创新是大型游乐设施占领市场的核心竞争力,但创新也容易引发各类问题及不确定性,特别是涉及游乐设备可维护性方面,更容易在创新过程中忽视。本文以国外设备供应商生产的“自由落体”游乐设备的故障入手,从研究直流电机故障机理、维修方案以及设计维保建议等几个方面,提出提升直流电机可维护性的举措,主张行业的设计人员不但要聚焦大型游乐设施的趣味性,也要更多关注如何提高大型游乐设施的可靠性、可维护性。     

不同减排情景下城市机动车污染防治措施研究

机动车数量的增加严重威胁城市环境,本文在不同减排情境下,开展城市机动车污染防治措施研究。使用清洁能源代替不可再生能源作为机动车动力燃料;明确责任制度,强化机动车管理体制,提升空气质量;布设城市监控设备优化交通结构,减少排放源;完善法律制度,协调经济发展与环保关系;发展公共交通,倡导绿色出行理念,降低城市机动车尾气排放污染。     

Validity of police-reported alcohol involvement in fatal motor carrier crashes in the United States between 1982 and 2005

Objective

To examine the validity of police-reported alcohol data for drivers involved in fatal motor carrier crashes.

Material and Methods

We determined the availability of blood alcohol concentration (BAC) and police-reported alcohol data on 157,702 drivers involved in fatal motor carrier crashes between 1982 - 2005 using Fatality Analysis and Reporting System (FARS) data. Drivers were categorized as motor carrier drivers if they operated a vehicle with a gross vehicle weight rating of greater than 26,000 pounds. Otherwise, they were classified as non motor carrier drivers. The sensitivity and specificity of police-reported alcohol involvement were estimated for both driver types.

Results

Of the 157,702 drivers, 18% had no alcohol information, 15% had BAC results, 42% had police-reported alcohol data, and 25% had both. Alcohol information varied significantly by driver, crash, and vehicle characteristics. For example, motor carrier drivers were significantly more likely (51%) to have BAC testing results compared to non motor carrier drivers (31%) (p < 0.001). The sensitivity of police-reported alcohol involvement for a BAC level ≥ 0.08 was 83% (95% CI 79%, 86%) for motor carrier drivers and 90% (95% CI 89%, 90%) for non motor carrier drivers. The specificity rates were 96% (95% CI 95%, 96%) and 91% (95% CI 90%, 91%), respectively.

Conclusions

The sensitivity and specificity of police-reported alcohol involvement are reasonably high for drivers involved in fatal motor carrier crashes. Further research is needed to determine the extent to which the accuracy of police-reported alcohol involvement may be overestimated because of verification bias.

Impact on the Industry

Based on the results of this study, the federal government should continue to work with states to strengthen their strategies to increase chemical testing of all drivers involved in fatal crashes.     

电梯电动机运转时间限制器检验新方法的探讨

随着电梯的广泛使用,钢丝绳断丝、断股导致的事故时有发生,电梯电动机运转时间限制器的重要性越来越凸显出来。针对电梯电动机运转时间限制器落后的检验现状,根据实际现场检验经验,通过分析电梯的控制原理,总结了一种新的检验方法,该方法安全性高,实用性强,操作方便。     

Assessment of medical care costs of injuries due to alcohol-related motor vehicle crashes

The purpose of this study was to estimate the total medical care costs of individuals injured in motor vehicle crashes and in crashes where alcohol was involved. Crashes were studied that involved 2,728 vehicle occupants and 191 pedestrians with injuries as reported in 1979 by the National Accident Sampling System, a probability sample of all motor vehicle crashes occurring in the united States. Medical care costs were assigned by using Abbreviated Injury Scale codes in accordance with other published research. Determination of alcohol involvement was based on crash characteristics. Results indicate that 20.2 % of medical care costs for motor vehicle crash injuries may be due to crashes where alcohol was involved. It was estimated that alcohol-related motor vehicle crashes cost between $434 million and $483 million in medical care alone in the United States in 1979.     

Behavioral Factors as Predictors of Motor Vehicle Crashes in Young Drivers

Gains in reducing mortality and morbidity from motor vehicle crashes can be achieved by understanding the behavioral factors that contribute to the elevated risk of motor vehicle-related injury and death. This study investigates the incidence, along with the effect of driver and behavioral factors, on the likelihood of motor vehicle crashes. Seventeen year old newly licensed drivers (n = 1277) in Perth, Western Australia, were recruited and followed over the first 12 months of driving. Using Cox proportional hazard analysis, driver and behavioral factors were assessed to determine whether they predicted the likelihood of a crash in the first 12 months of driving. The crash incidence rate was higher for males (1R = 4.6/10,000 driving days) than females (IR = 3.9/10,000 driving days). Multivariate analysis indicated that drivers who reported to have driven daily prior to obtaining their learners permit (L-plates) were at an increased risk of motor vehicle crash. A twofold increase in motor vehicle crash was apparent among drivers considered to be confident-adventurous drivers compared to low to moderate levels of driver confidence-adventurousness (HR = 2.04, 95% CI = 1.29-3.21). The research indicates that a driver's perception of their confidence and adventurousness in the road environment plays a part in the causal pathway leading to a motor vehicle crash. This research points to the need for preventive strategies that focus not only on knowledge and skill acquisition, but also the driver's perception in preparing young people for our roads.     

County-level prohibition and alcohol-related fatal motor vehicle accidents

The 50 states and the District of Columbia were grouped according to whether or not they had county-level alcohol prohibition. Several motor vehicle fatality rates were calculated for each type of jurisdiction, including the single-vehicle fatality rate (an index of alcohol-related motor vehicle accidents). In all cases, motor vehicle fatality rates for drivers in states with county-level prohibition were significantly greater than in nonprohibition states. This suggests that drivers residing in counties with prohibition are compelled to drive to adjacent counties or states to drink and consequently have increased involvement in motor vehicle accidents.     

Behavioural reactivation and subjective assessment of the state of vigilance--application to simulated car driving.

The frequency of some behaviour (such as self-centred gestures) increases during a task that leads to the occurrence of low-vigilance episodes. These gestures can be useful in stimulating oneself. A study carried out in 20 adults has enabled us to state that motor activity (recorded with an actimeter) increases with the duration of a monotonous driving task and sleep deprivation. The analysis of the scores recorded using the Karolinska Sleepiness Scale has shown that drivers can assess the deterioration of their state of vigilance according to the actual sleep preceding the driving test. Finally, the joint analysis of the subjective and objective data revealed a co-variation of these two types of indices. We discuss the stimulatory function of the motor activity in a task leading to the occurrence of low-vigilance episodes by investigating, among other things, the use, conscious or not, of this type of activity.     

直线电机轮轨交通系统安全性分析

直线电机轮轨系统采用直线感应电机牵引 ,轮轨系统支承导向 ,是一种在技术、经济、环保方面均具有良好性能的新型城市轨道交通系统。该系统有两种主要技术模式 ,均有良好的安全运营记录。笔者介绍了系统的性能和设计特点 ;从牵引制动系统、控制系统、管理系统、养护维修系统以及防灾系统 5个方面对系统的安全性设计方法进行了总结 ;认为该系统具有良好的安全性能 ,先进的安全管理理念以及健全的安全防护系统 ;特别强调对该系统进行的安全设计研究 ,将为提高我国城市轨道交通系统的安全性提供新的思路