[360] How to keep the power catenary in close contact with pantograph

In the course of the train operation, the total hope is that the pantograph and the contact line can always keep close contact. In principle, the best relationship between the bow net is to let the current from the catenary reliable and stable "leakage" to the pantograph, so when the pantograph rises, "The electrical bow and the power grid contact location Leakage" worry is not necessary. And should be avoided by the pantograph and locomotive connection of the supporting insulator leakage, generally due to the insulator pollution, commonly known as roof "blasting", will affect the normal use of locomotives. The pantograph is dependent on a certain lift lift to keep the skateboard in contact with the contact line. When the train is running at high speed, the pantograph's skateboard is like a small airplane wing, and the effect of air flow will produce a dynamic lift, and lift lift increases with the speed of the train running. In the train operation, the contact line under the action of the pantograph lift up and down vibration, vibration wave forward, which gives the pantograph and contact line to maintain good contact has brought difficulties. The closer the speed of the pantograph is to the velocity of the contact line, the more likely it is to lose contact by the pantograph and the contact line. The phenomenon of loss of contact between the pantograph and the contact line is called "Offline". Offline is definitely not welcome. Because the high-speed train's pantograph from the contact line to obtain a large current value, the arc generated when offline (just like when we unplug the wire at home will produce electrical sparks) will speed up the pantograph skateboard and contact line wear, causing electromagnetic interference, but also accompanied by noise pollution. The more times you take offline, the longer it is, indicating that the quality of the stream is worse. Therefore, the general use of "off-line rate" to evaluate the quality of the train flow. The off-line rate is expressed as a percentage of the running time of the train zone by offline time. For example, the Beijing Tianjin intercity Railway requires offline rates below 0.14% and offline for less than 100 milliseconds. How can you reduce the offline rate? In the case of contact suspension, the contact line and pantograph should be worked out. The faster the wave propagation speed of the contact line and the closer the train speed, the easier it takes to go offline. Therefore, we can improve the speed of transmission of the contact line, as far as possible to "avoid" the speed of the train, you can significantly reduce the offline rate. Wave propagation speed to "hide" how far it is good. Experience shows that the ratio of train speed to wave propagation speed is between 0.6~0.7, which can guarantee good flow quality. For example, when the Beijing-Tianjin Inter-Railway train speed is 350 km, the contact line fluctuation propagation speed of 569 km/h, the ratio of the two is 0.62, to meet the flow quality requirements. In order to improve the train speed under the precondition of good flow, it is a powerful means to improve the speed of wave propagation, and there are two measures: one is to increase the tension of the contact line, and the other is to reduce the contact line quality of the unit length, which is the best use of light material in the contact line. Increasing the lifting force of pantograph and reducing the quality of pantograph can also improve the quality of flow. However, the increase of the pantograph lift has a certain limit, increase lifting lift Although the pantograph can be better to paste the contact line, but also speed up pantograph slide and contact line wear, easy to increase the contact line metal fatigue, shorten its life. Therefore, the lifting force of pantograph should be considered comprehensively and selected rationally to obtain the best result. The biggest difference between the high-speed bow and the ordinary bow is that the offline rate is small at high speed and the flow is more stable. Mainly by the lighter bow quality and better contact performance of the bow net to ensure. When the electric locomotive runs at constant speed, the reliable contact between the pantograph and the catenary can be maintained, thus guaranteeing a good dynamic flow between the pantograph and the catenary. However, with the high speed electric locomotive running speed increase, will make the pantograph vibration intensified, the occurrence of frequent off-line phenomenon, deterioration of the pantograph by the flow of quality, so that the speed of the locomotive is limited. In order to improve the dynamic characteristic of electric locomotive pantograph, reduce the vibration, reduce the off-line rate between pantograph and catenary, the wire rope damper with hysteresis nonlinearity is used in the bow head suspension, and good damping effect is achieved in practical application. In view of the characteristics of high-speed train pantograph and catenary system, combined with the corresponding evaluation criteria (off-line rate, contact pressure, elasticity, etc.), many experts discussed and analyzed in detail some technical problems such as clue, hanging string, positioning device, electric phase device, tension compensation device and anchor joint of high-speed railway catenary suspension. In order to adapt to the high speed development of railway, reduce the wear of catenary wire, the working conditions of pantograph skateboard under pantograph slide have random change of load, strong current passing through the contact, high sliding speed, complex and changeable environment conditions, and other notable features. Therefore, the selection of its material has very stringent requirements. With the continuous development of new materials and development of applications, we can believe that in the near future, the use of pantograph skateboard materials are mainly carbon skateboard, copper-based powder metallurgy skateboard and metal-impregnated carbon skateboard, will gradually to carbon fiber, metal fiber, with lubricating function of metal-based and inorganic non-metallic matrix composites development. At present, the widely used catenary wire has copper silver, copper tin, copper magnesium contact wire, will be to copper alloying and compound metallization direction development. Under the premise of the catenary, pantograph skateboard should generally meet the good electrical conductivity, suppress the generation of off-line arc and arc burn resistance, good antifriction and abrasion resistance, sufficient strength and strong adaptability to the natural environment and other performance requirements. At present, some experts in our country have developed a new pantograph skateboard by powder metallurgy method by analyzing various problems existing in electric locomotive pantograph skateboard. Copper-graphite composite is an ideal self-lubricating and conductive material, and it is an ideal material for preparing electrical contact elements such as electric locomotive pantograph skateboard. The skateboard is composed of copper, carbon fiber and graphite. The influence of forming pressure and sintering temperature on the performance of the skateboard is analyzed, and the electric conductivity, friction, wear performance and impact toughness are tested, and compared with the pantograph slide plate currently being used. The results show that the optimum preparation process of the new type skateboard is (content) copper 78%, carbon fiber 2%, graphite 15%, additive 5%, forming pressure is 200MPa, sintering temperature is 880 ℃. The board not only has low resistivity, but also has superior properties such as friction, wear and impact toughness to the Pantograph skateboards currently in use. Compared with foreign dip metal carbon slide rh82mb, the friction coefficient is reduced by 20%, the wear volume is reduced by 1.3%, the impact toughness is increased 1.7 times times, and the conductivity is increased 65 times times. Http://www.51crh.com/thread-126983-1-1.html

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