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拖拉机中央传动及转向离合器设计,拖拉机,中央,传动,转向离合器,设计
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电力机车简介 机车是为列车提供驱动力，而自身并没有效装载能力的车辆；他的唯一目标是沿着轨道牵引列车。通常自带动力的车辆不被视为机车，在客运方面自带动力的车辆用得越来越普遍，但是很少用在货运。自带驱动力的车辆以驱动列车的车辆，通常它们不视为机车，因为它们具有有效装载能力，并且很少从列车上摘挂，它们称之为动车。一般来说，机车牵引列车。现今在客运业务上拖拉式运营方式越来越常见，采用这种运营方式的特点是：机车在一端牵引列车，然而却由在另一端的司机室控制。机车的优点：在一般情况下,为什么将为列车提供驱动力的机车和车辆是分开的，而不是车辆自带动力的原因包括以下几点：1 易于维修维修一台机车和维修自带动力的车辆相比要容易。2 安全通常将列车牵引动力装置安装在远离乘客的地方比较安全，这一点对于蒸汽机车来说显得相当重要，但是有时会仍然会出现一些不如意的情况。3 易于更换动力如果动力装置损坏，用一个新的来更换它即可，这样地来显得比较容易，从而一个动力装置产生故障时不至于整台机车无法工作。4 效率当列车空载运行时可以将机车从列车上摘卸下来。机车再去执行其它牵引业务，这意味着不但可以降低列车运营成本，还可以提高机车的使用效率。 5.将机车和车辆分离开来意味着当机车出现故障时，只需更换机车就可以这样就可以不影响列车的运营。在有些情况下车辆比机车先报废，如果机车和车辆不可摘挂，那么即使机车完好也得跟着报废，这样就意味着浪费和成本高，然而机车可以从列车上摘下来，只需更换车辆即可，这样五来大大的降低了成本提高了经济效益。电力机车电力机车是通过接触网或第三轨由外部提供电能。尽管电气化铁道的造价相当高，然而运营成本却比内燃机车低，良好的加速性能和可再生制动，使得它们在繁忙干线地区成为客运业务的理想选择。几乎所有的高速铁路都采用电力牵引（例如ICE，TGV），由于具有如此高的性能，机车所需要的电能是不容易得到提供。例如应用在海底隧道货运业务的现今最大功率的机车的功率高达7MW。第一台电力机车由Scotsman和Robert Davidson于1837年设计并生产，该电力机车由电流单元提供动力。现代电力机车包括从由蓄电池提供能量的用于矿山的机车到功率高达6000马力(4.5M)甚至功率更高的干线电力机车。事实上，现代许多机车它们是电力驱动的，纯电力机车是从外部获得电能，然而内燃电力机车它们却自带发电装置。干线电力机车第一次出现在20世纪初，电力机车的诞生是由于蒸汽机车产生在运行过程产生的烟雾给驾乘带来不便和不安全，特别是在隧道。在英国引入电力机车的是由于地铁系统的需要。然而在美国引入电力机车却是由于河底隧道这样一个特殊的工作环境下采用内燃牵引无法满足要求。早期电力机车全都依靠外部提供电能，尽管它们运行可靠和效率高，但是建造接触网是一笔相当大的投资，并且需要不断维护。基于此，电气化铁道仅仅在繁忙干线采用。在市郊采用电气化铁道可以减轻由蒸汽机车燃烧所带来的粉尘污染。世界列车最高运行速度纪录由法国TGV在1990年创立。速度高达515.3千米每小时(320mph)。然而，近来所设计的电气化铁道几乎都采用交流制，当然许多已有的直流供电制仍然在用，例如：南非，西班牙，英国（750V和1500V），挪威（1500V），安哥拉，意大利，波兰（3000V），芝加哥和Mumbai（它们将由2025转换成交流供电制）。早期的机车有各种型式。通常它们设计成与供电制相匹配的机车。于是采用直流供电制的电气化铁道的铁路系统，电力机车的牵引电机为直流电机。采用交流供电制的电气化铁道的铁路系统，电力机车的牵引电机为交流电机。交流可以是单相，也可以是三相，单相需要两根导线，一根是接触网，另一根是钢轨。三相需要三根导线，因此三相电力机车有两根接触网，钢轨作为第三根。直流供电可以用接触网或钢轨供电，通常称之为第三轨。交流牵引电机体积比直流牵引电机的体积小。通常这就意味着直流电机可以做得体积小些。安装驱动轴，通常采用齿轮传动。但是在早期也有采用轴的。即便如此，一些著名的直流电力机车采用直流电动机驱动车轮。采用电力机车作为牵引动力的一种可能就是在制动期间电动机可作为发电机并把发出的电能反馈给接触网，这种被称之为再生抽动。这是一个新的想法，这就是三相交流供电制为什么要采用的原因。特别是在山区，机车下坡时产生的能量以供机车使用。瑞士铁路采用这种系统。三个下程供给一个上程。现今，所有电力机车都趋于将驱动电机安装在靠近车轮轴的位置，尽管仍有些电力机车将驱动电机安装在车体内通过传动装置来驱动车轮。现代实体状态电控系统的采用意味着电机并不需要和供电制相匹配。因而在今天，多电压等级的机车已相当普遍。通常驱动电机是直流电机，但是在一些机车上也有三相驱动电机。蓄电池机车在矿场和由内燃机产生的烟是一个不安全隐患的其它地下作业和外部电能不可获得的情况下利用。蓄电池机车在许多地铁系统当供电被暂时切断而需要维修作为维修作业车。电力机车的各组成部分:异步电动机现代牵引电机主要采用三相牵引电机,并被广泛应用于现代列车牵引系统.采用适当的控制电子装置后,三相牵引电机可以用在直流或交流制的电气化铁道和内燃机车.电池所有的列车都备有电池以提供起动电流和为一些装置提供电源,例如当接触网供电失败时的紧急照明,通过电池是和直流控制供电装置相连.断路器电力机车通常备有一定型式的空气断路器以将从接触网隔离,当机车发生故障,或者需要维修时。在交流制供电式中，断路器通常安装在机车顶部靠近受电弓的一侧。现有两种类型的断路器：空气断路器和真空断路器（VCB）。空气或真空是用来灭当断路器的两连接端分开时产生的电弧。真空断路在英国用得比较多，而空气断路器在欧洲大陆用得比较广泛。逆变器将交流转变成直流称之为整流，将直流转变成交流称之为逆变。逆变这一词起源于美国，但是现在这一学术用语在其它地方也被用。冷却风扇为了冷却整流装置和其它电子装置，现代机车都装有空气管理系统，电子控制装置使所有的系统都运行在允许的温度范围内。风扇由一台产生400伏电源的三相交流的辅助逆变装置供电。直流连接器在三相和单相整流器中，直流连接器用在现代电子电源系统中。通过将交流电整流成直流，然后将直流逆变成三相交流，很容易将从接触网获得的单相交流电转变成所需要的三相交流电。线路断路器在列车上安装电力电子器件可将直流电转换为交流电。当今采用直流供电制的铁路系统也广泛采用三相牵引电机和一些辅助设备也采用三相交流电。电子机械开关安装在牵引电机上电子机械式开关以断开和接通牵引电机电路，通常情况下开关是闭合的。它受牵引控制器的指令控制，而并非电压检测传感器的控制。它和过载检测装置和非电压控制电路相连接以便在发生过载时切断电机电路以保护牵引电机。司机控制器驱动力控制装置安装在司机室。司机移动司机操纵手柄以提高或减小机车牵引力。牵引电机冷却风机电力机车上的牵引电机很容易发热，牵引电机在长时间满负荷运行式况下，为了使其温升在允许的范围内，通常给牵引电机安装有风扇称之为冷却风机。在现代机车上，风扇由一台产生400伏左右电源的三相交流辅助逆变装置供电。整流器整流器由将交流转换为直流的可控硅和二极管组成。通常现代电力机车至少有两个整流器，一个用于主电路的整流，一个用于辅助电路的整流。同步电动机牵引同步电机是 励磁线圈安装在驱动轴上 电枢线圈安装在定子上的电机, 这和通常的电机刚好相反。这种电机在广泛应用在法国用于高速列车用得由法国和它采用了高速的TGV大西洋列车 这是一种由简单逆变器控制的单相电机。现在已被异步电动机取代了 。变压器变压器是由铁芯和绕组组成且将电压由一个等级升高或降低到另一个等级的设备。变压器的输出电压由输入侧和输出侧绕组匝数之比决定。变压器作为电力机车不可缺少的设备其将从接触网的电压变换成机车在牵引工况下所需电压。Introduction to LocmotiveA locomotive is a railway vehicle that provides the motive power for a train,and has nohy detached from their trains, are known as power cars.Traditionally,locomotive hual their trains. Increasingly common these days in passenger service is push-pull operation,where the locomotive push the trains in one direction and are controled from a control cab at the opposite end of the train in the other.Beniefits of locomotivesThere are many reasons why the motive power for trains has been traditonally isolated in a locmotive,rather than is self-propelled vehicles.these include:Ease of maintenance it is easier to maintain one locomotive than many self-propelled cars.Safety it is often safer to locate the trains power system away from passenger. This was particularly the case for the steam locomtive,but still has some relevance.Easy replacement of motive power should the locomotive break down, it is easy to replace it with a new one . Failure of the motive power unit does not require taking the whoole train out of service.Efficiency idle trains do not waste expensive motive power resources. Separate locomotives mean that the costly motive power assets can be moved around as needed.Obsolescence cycles separating the motive power from the payload-hauling cars means that either can be replaced without affecting the other. At some times, locomotive have become obsolete when their cars are not, or vice versa.Electric LocomotivesThe electric locomotive is supplied externally with electric power, either through an overhead pickup or through a third-rail. While the cost of electrifying track is rather high, electric trains and locomotives are significantly cheaper to run than diesel ones, and are capable of superior acceleration as well as regenerative braking, making them ideal for passenger service in densely populated areas. Almost all high speed train systems(e.g.IEC,TGV, bullet train) use electric power, because the power needed for such performance is not easily carried on board. Fot example the most powerfu electric locomotives that are used today on the channel tunnel freight services use 7Mwatts of power.The first known electric locomotive was buit by a Scotsman, Roert Davidson of Aberdeen in 1837 and was powered by galvanic cells.Modern electric locomotive range from small battery-powered machines for use in mines to large main-line locomotives of 6,000 horsepower(4.5MW) or more.In reality most modern locomotives are electricaly driven. Pure electric locomotives take their electrical supply from an external source while diesel-electric locomotives carry their own generating station.Main line electric locomotives first appeared at the beginning of the 20th century.The reason for their introduction was the problem of smoke, especially in tunnlels caused by steam locomotives. In the UK this was the London underground system while in the USA, it was under river tunnles and needs to eliminate smoke in built up areas.Early electric locomotives all relied on external power sourcing. Once up and running they tend to be reliable and efficint, but the supply infrastructure is a large capital expense that does require ongoing maintenance. For this reason only heavily used lines could justify electrification. For suburban lines the reduction in pollution from steam locomotives was a benefit all were aware oflThe world speed record for a wheeled train was set in 1990 ba a French TGV which reached a speed of 515.3km/h (320mph).While recently designed electrififed railway systems invariably operate on alternating current, many existing direct current sytems are still in use e.g. in South Africa,Spain,and the United Kingdom(750v and 1500v); Netherlands(1500v); Belgiu, Italy, Poland (3000 v), and the cites of Mumbia and Chicagio (which will be switched to AC by 2025).Early locomotives came in a variety of forms. Generally they were designed to run off the supplied current. so locomotives with a direct current (DC) supply had DC motors while a alterntating current(AC) supplied locomotives with AC motors. AC can be either single or three phase. While the former requies two wire supply, one overhead the other being the track, three phase require three supply wire.Three phase locomotives therefore had two overhead supplies,the track being the third.DC supplies were either overhead or by means of a track level supply, commonly called the third rail.AC traction motors tended to be smaller than DC motors. This often meant electric locomotives with steam engine type cranks. DC motors could be smaller and set up to drive the axles.usually through a gear ,but in some early examples by being part of the axle. Even so, some notable DC electric locomotives had large DC motors driving large driving wheels. One possibility with electric locomotives is that the motor can be used as a generator during braking, feeding electricity back into the supply system; this is called regenerative barking. This is not a new idea, it was one reason for the adoption by some railways of 3 phase AC suppies. Especially in mountainous aresa where the locomotive going down would generate much of the suppy for a locomotive going up. The Swiss railway uses the system; three modern locomotives heading downwards generate enough power to power a single locomotive in its upward journey.Today all eclctric locomotives tend to have drive motors close to the axles, although some still have the motor in the body driving the wheels through internal drive shafts.Modern solid state electrical control systems means the motor does not need to match the supply. This meams multi-voltage cross border locomotives are now quite common. Drive motors are generally DC, but there are 3 phase motors on some locomotives.A small number of electric locomotives can also operate off batery power to enable short journeys or shuting to occur on non-electrified lines or yards. Pure battery locomotives also found usage in mines and other underground workings where diesel fumes or smoke are not safe aand where external electricity supplies could not be used. Battery locomotives are also used on many underground railways for maintenance operations as they are required to operate in areas where the electricity supply has been temmporarily disconnected.Parts of Electric LocomotiveAwynchronoux Motor Modern traction motor type using three phase AC electrical supply and now the favoured deisgn for modern train traction systems . Can be used on DC and AC electrified. railways with suitable control electronics and on diesel-electric locomtives.Axle BrushThe means by which the power supply ciruit is completed with the substation once power has been drawn on the locomotive. Current collected from the overhead line or third rail is returned via the axle brush and one of the running rails. Battery All trains are provided with a battery to provide start up current for supplying essential circuitts, such as emergency lighting ,when the line supply fails. The battery is usually connected across the DC control supply circuit.Circuit BreakerAn electric train is almost always provied with some sort of circuit breaker to isolate the power supply when there is a fault, or for maintenance. On AC systems they are usually on the roof near the pantograph. There are two types-the air blast circuit breaker and the vacuum circuit breaker or VCB. The air or vacuum part is used to extinguish the arc which occurs as the two tips of the circuit breaker are opened. The VCB is popular in the UK and the air blast circuit breaker is more often seen on the continent of Europe.Converter Generic term for any solid state electronic system for converting alternating current to direct current or vice versa. Where an AC supply has to be converted to DC it is called a rectifier and where DC is converted to AC it is called an inverter. The word originated in the US but is now common elsewhere.Cooling Fans To keep the thyristors and other electronic power systems cool, the interior of a modern locomotive is equipped with an air management system, electronically controlled to keep all systems operating at the correct temperature. The fans are powered by an auxiliary inverter producing 3-phase AC at about 400 volts.DC link Used on modern electronic power systems between the single phase rectifier and the 3-phase inverter. It is easier to convert the single phase AC from the overheak line to the 3-phase required for the motors by rectifying it to DC and then inverting the DC to 3-phase AC.InverterElectronic power device mounted on trains to provide alternating current from direct current. Popular nowadays for DC railways to allow three phase drive or for auxiliary supplies which need an AC supply.Line BreakerElectro-mechanical switch in a traction motor power circuit used to active or disable the circuit the circuit. It is nomally closed to start the train and remains closed all the time power is required. It is opened by a command from the driving controller,no-volts detected, overload detected and (were required) wheel spin or slide detected. It is linked to the overload and no-volt control circuits so that it actually functions as a protective circuit breaker.Master Controller Drivers power control device located in the cab. The driver moves the handle of the master controller to apply or reduce power to the locomotive or train.Motor BlowersT
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