城市轨道交通专业英语 课程教案（第16周3—4节）
授课题目
Unit 4  Power System and Electricity Equipment
Lesson 3 Overhead Catenary Traction System（下）
授课类型
讲授型
教学目标
Master the knowledge of all Sort (s) of Catenary Suspension Systems and pantographs
重  点
.All Sort (s) of Catenary Suspension Systems
.pantographs
难  点
It can cause the dropper wires, from which the contact
wire is hung, to " kink" and form little loops.
the dropper wires是宾语， from which the contact wire is hung 是介词短语，说明the dropper wires 的作用, to "kink" and form little loops是补语，进一步说明后果。
教学过程
 
结合课文以及教材中给出的图例，详细讲述文章中所描的
高架链型牵引网系统中的各种形式的链型悬挂系统、受电弓等方面的相关知识以及文中生词、短语、及语法结构
作  业
1.New Words and Expressions
2. Notes on the text
主
要
教
学
内
容
2. All Sort (s) of Catenary Suspension Systems各种形式的链型悬挂系统
Various forms of catenary suspension are used (Fig. 4-14) , depending on the system, its age, its location and the speed of trains using it. 根据特定的系统、它的使用年限、使用区域以及使用列车的速度，各种形式的链形悬挂系统得到了应用（图4—14）。
Broadly speaking, the higher speeds, the more complex the "stitching" , although a simple catenary will usually suffice if the support posts are close enough on a high speed route.广而言之，速度越高，接触网越复杂，在一条高速线路上，如果支柱足够近，一个简单链型悬挂就能满足需要。
Modern installations often use the simple catenary , slightly sagged to provide a good contact.现代化的设备经常用简单链型悬挂，下垂度微小，可以提供良好的接触。
It has been found to perform well at speeds up to 200 km/h.已经发现，在速度高于200 km/h时，它也能很好地工作。
A tram depot may have just a single wire hung directly from insulated supports. 一个有轨电车供电线仅有一条接触线，它直接悬挂在绝缘支持设备上。
As a pantograph passes along it, the wire can be seen to rise and fall.当受电弓通过它时，能够看到接触电线升起和落下。
This is all that is necessary in a slow speed depot environment.在低速环境下，它是足够的、满足要求的。
We haven't yet mentioned trolley poles as a method of current collection. 我们没有把电车电极作为一种受电方式。
These were used for current collection on low speed overhead systems and were common on trams or streetcars but they are now obsolete.这些一般应用在低速高架接触网系统，而且在有轨电车和路面电车中是常见的，但是现在它们是陈旧的技术。
DC overhead wires are usually thicker and, in extreme load cases, double wires are used, as in Hong Kong Mass Transit's 1500 V DC supply system.高架接触线常常很粗，在特殊负载情况下，采用双接触线，香港市内公
交通1500V DC供电系统就是这样的。
Up to 3000 volts overhead is used by DC main line systems ( e. g. parts of France, Belgium and Italy) , but below 1500 volts, a third rail can be used.sort of是什么意思英语高达3000v的高架接触线常常应用在直流干线系统 （ 如法国、 比利时和意大利的部分铁路 ） ， 但是1500V 以下的直流系统 ， 可以采用第三轨。
In operating terms, the third rail is awkward because of the greater risk of it being touched at ground level.在运行期间 ， 第 三轨比较笨拙， 因为要冒着在地面 上接触到它的危险。
It also means that, if trains are stopped, the current has to be turned off before Passengers can be allowed to wander the track. 也就意味着 ， 如果列车停了下来 ， 在允许乘客在轨道上徘徊之前 ， 电流必须被切断 为了100％的安全。
Third rail routes need special protection to be completely safe. 第三轨线路需要特殊的保护。
On the other hand, some people consider the overhead catenary system will produce a visual intrusion.另一方面 ， 一些人认为高架接触网系统 （ 产生 ） 视觉的干扰。
Singapore, for example, has banned its use outside of tunnels.例如 ， 新加坡已经禁止在隧道外使用高架系统。
3 pantographs 受电弓
  current is collected from overhead lines by pantographs.机车从高架线通过受电弓获得电流。
Pantographs are easy in terms of isolation—you just lower the pan to lose the power supply to the vehicle.受电弓很容易就可以将机车与高架线断开， 你只需降低受电弓，让车辆失去电能。
  Since the pantograph is usually the single power contact point for the locomotive or power car. 对于列车或者电力机车而言 ， 受电弓是唯一的电力接触点 。
it maintain good contact under all running conditions. 在任何运行状况下 ，它必须保持良好的接触。
The higher the speed is, the more difficult maintenance of good contact. 列车速度越高 ， 保持良好的接触就越困难。
We have already mentioned the problem (above) of a wave being in the wire by a pantograph moving at high speed. 前面我们已经讨论了这个问题 ， 这是由于受电弓的高速移动血在接触线上形成的波动问题。
pantograph contact is maintained either by spring or air pressure.受电弓接触依靠弹性力或者气体压力来保持良好的接触。
Compressed air pressure is preferred for high speed operation. 对于高速运行系统 ， 首选压缩空气压力 。
The pantograph is connected to a piston in a cylinder and air pressure in the cylinder maintains the pantograph in the raised condition.受电弓和一个活塞相连 ， 活塞安装在气缸内 ， 而且在气缸内的空气压力维持受电弓在升起的状态。
Originally, pantographs were just that, a diamond-shaped pantograph" with the contact head at the top. 在车的顶部，最初的受电弓只是一个带着接触头的菱形形状的受电弓。
Two contact faces are normally provided. 通常提供两个接触面。
More modern systems use a single arm pantograph—really just half of the original shape—a neater looking design ( photo above) .更现代化的系统用一个单臂受电弓，实际上仅仅是原来形状的一半，一个整洁好看的没计。
  The contact strips of the pantograph are supported by a lightweight transverse frame which has "horns" at each end ( Fig. 4-15) .受电弓的接触面被一个重量较轻的横向构架支撑着，在每个的末端这个横向构架有一个羊角 （ 图4-15 ） 。
These are turned downwards to reduce the risk of the pantograph hooked over the top of the contact wire as the train moves along.  这些羊角向下弯转 ， 当列车在运行时 ， 就可以减少钩挂上面接触线的危险。
This is one of the most common causes of wires "being down" .这是一个最常见的造成接触线落下的原因之一。
A train moving at speed with its pantograph hooked over the wire can bring down several kilometres of line before it is detected and the train stopped.  以一定速度运行的列车 ， 如果它的受电弓钩在接触线上 ， 在发现它之前和列车停下之前， 能够拉断几公里的接触线。
The most sophisticated pantographs have horns which are designed to break off when struck hard。  最精致的受电弓设计有在严重撞击下可折断的触角 。
for example, by a dropper or catenary support arm. 例如 ， 遭到落下物或者悬链式腕臂的撞击。
These special horns have a small air pressure tube attached which, the pressure is lost, it will cause the pan to lower automatically and so reduce the possible ware damage.这些特殊的触角有一个小的空气压力管附在它的上面，如果压力消失，会引起受电弓自动下降，这样可以减少接触线损坏的可能。
教学小结
本节课主要介绍了高架链型牵引网系统中的各种形式的链型悬挂系统、受电弓等方面的内容，同学们对此非常陌生，要仔细讲解。

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