The Railway Technical Website > 자유게시판

Each length is overlapped by its neighbour to ensure a smooth passage for the "pan". Each subsection is remoted from its neighbour by a piece insulator within the overhead contact as proven on this image below. The weights and pulley system is designed to keep up contact wire tension. The contact wire must be held in tension horizontally and pulled laterally to negotiate curves in the observe. The contact wire tension will be within the region of two tonnes. The contact strips of the pantograph are supported by a lightweight transverse body which has "horns" at every finish. Of course there are exceptions and we will see some of them later. An electric arc occurs with every bounce and a pan and wire will soon each become worn by way of underneath such situations. As AC is less complicated to transmit over lengthy distances, it is a perfect medium for electric railways. Some train services operate over traces utilizing multiple type of present. This is one of the most common causes of wires "being down".

DC overhead wires are often thicker and, in excessive load instances, double wires are used, as in Hong Kong Mass Transit’s 1500 v DC supply system. In cities equivalent to London, New York City and Boston, the same trains run under overhead wires for part of the journey and use third rail for the remainder. Figure 9: To reduce the arcing at a neutral part within the overhead catenary, some techniques use track magnets to routinely switch off the facility on the prepare on the method to the impartial part. The wire is zigzagged relative to the centre line of the track to even the put on on the practice's pantograph as it runs beneath. The French TGV (High Speed Train) formation has a power automotive at every end of the train however solely runs with one pantograph raised underneath the high speed 25 kV AC lines. The rear automobile is provided by a 25 kV cable working the size of the practice. The effect of this association is to cut back the noise ranges in the communications cable and make sure the voltages remain at a protected level.

In Europe, some locomotives are outfitted to operate underneath 4 voltages - 25 kV AC, 15 kV AC, what is electric cable 3,000 V DC and 1,500 V DC. These are positioned on masts at intervals along the route. The return conductor is related to the running rail at intervals to parallel the return cable and rails. They're related to the feeder station by a return conductor cable hung from the masts so that it's roughly the same distance from the track because the overhead line. There needs to be a whole circuit, from the supply of the power out to the consuming merchandise (mild bulb, cooking stove or practice) and again to the source, so a return conductor is required for our railway. What in regards to the electrical return? If a communications cable is laid alongside rails carrying the return present of the overhead line provide, it might probably have unequal voltages induced in it. It can be summarised simply as AC for long distance and DC for short distance. Of course, it needed a heavier transmission medium, a third rail or a thick wire, to carry the facility and it lost a good amount of voltage as the distance between supply connections increased.

Provided precautions are taken to forestall the voltage getting too excessive above the zero of the ground, it works very effectively and has accomplished so for the last century. Broadly talking, the upper speeds, the more complicated the "stitching", although a simple catenary will often suffice if the help posts are close sufficient together on a high velocity route. The mechanics of power provide wiring shouldn't be as easy as it seems to be (Figure 1). Hanging a wire over the monitor, providing it with current and operating trains below it isn't that simple whether it is to do the job correctly and final lengthy enough to justify the expense of installing it. Figure 11: A schematic exhibiting the arrangements for 25kV AC electrification systems using booster transformers (upper drawing) and the auto transformer system (lower drawing). Figure 7: Overhead contact wire displaying the grooves added to supply for the dropper clips. Figure 12: Russian video of a pantograph being damaged by an overhead wire out of place. A couple of pantograph on a prepare may cause the same drawback when the leading pantograph head sets up a wave within the wire and the rear head can’t stay involved. Originally, pantographs have been just that, a diamond-shaped "pantograph" with the contact head at the top.