The principle of maglev train suspended in the air ~ ~ ~

The principle of maglev train is not profound. It uses the property of "like-sex repulsion and opposite-sex attraction" to make the magnet have the ability of defying gravity, that is, "magnetic levitation". Scientists apply the principle of "magnetic levitation" to the railway transportation system, which makes the train completely off the track and float, becoming a "wheelless" train with a speed of more than hundreds of kilometers per hour. This is the so-called "maglev train", also known as "magnetic cushion car".

Because the magnets have two forms: like repulsion and opposite attraction, the corresponding maglev train also has two forms: one is a maglev train with electromagnetic operation system designed by using the principle of like repulsion of magnets, which suspends the car body by using the repulsion between the magnetic field formed by superconducting electromagnets on the train and the magnetic field formed by coils on the track; The other is a maglev train with electric power operation system, which is designed by using the principle that magnets attract each other. Magnets are installed on the underbody and the upside-down top.

Iron, induction plate and induction steel plate are respectively installed above the T-shaped guide rail and below the leg part to control the current of the electromagnet, so that a gap of 10- 15 mm is maintained between the electromagnet and the guide rail, and the attraction of the guide rail steel plate is balanced with the gravity of the vehicle, so that the vehicle body is suspended on the guide rail surface of the driveway.

Compared with today's high-speed trains, maglev trains have many incomparable advantages:

Because the maglev train runs on the track, there is no actual contact between the guide rail and the locomotive, which becomes a "wheelless" state, so there is almost no friction between the wheels and the track, and the speed is as high as several hundred kilometers per hour;

Maglev train has the advantages of high reliability, simple maintenance and low cost, and its energy consumption is only half of that of automobiles and a quarter of that of airplanes.

Low noise. When the speed of maglev train reaches more than 300 kilometers per hour, the noise is only 656 decibels, which is only equivalent to a person talking loudly, which is smaller than the sound of a car passing by.

Because it is driven by electricity, it will not discharge waste gas along the track and there is no pollution. It is a veritable green means of transportation.

How does the maglev train work?

Maglev train is a high-tech means of transportation that uses the attraction and repulsion of magnetic poles. Simply put, repulsion makes the train suspended, and gravity makes the train move. Superconducting magnets are installed on the carriages of the maglev train, and coils are installed at the bottom of the railway. After electrification, the polarity of the magnetic field generated by the grounding coil is always the same as that of the electromagnet in the carriage, and the two are "the same polarity repels each other". The repulsive force makes the train float, which is different from the power of the conventional train from the locomotive head. The power of maglev train comes from the track. Coils are installed on both sides of the track. Alternating current turns the coil into an electromagnet, which interacts with the magnet on the train. When the train is running, the magnet (N pole) in front of the train is attracted by the electromagnet (S pole) in front and repelled by the electromagnet (N pole) behind? d？ d？ D the result is "pulling" in front and "pushing" behind, which makes the train move forward. When the train reaches the position shown in the figure, the current flowing in the coil is reversed. The result is that the original S-pole coil is now an N-pole coil, and vice versa.

When the maglev train is running, it should always keep a gap of 10 cm with the track. Any deviation is very dangerous to the stability of the train. But the magnetic field solved this problem. Because the magnet at the bottom of the track and the magnet on the carriage have the same polarity, there is always repulsive force between them. If the suspension of the train exceeds 10 cm for some reason, it means that the train has moved to an area where the magnetic field generated by the track is gradually weakened, so the obtained suspension force is reduced and the train will fall back to the height of 10 cm. On the contrary, if the train is too close to the track, it will encounter great resistance from the track magnetic field and get greater repulsive force, so that the train can keep a normal distance from the track. This eliminates the need to monitor the floating distance.

The biggest advantage of maglev train is its high speed, which can reach 400? D550, by adjusting the current intensity flowing through the magnet, the speed of the train can be changed conveniently. The traditional wheel-rail train has been developed for more than 100 years, with a top speed of only 300? If the speed of D350 is further increased, it will be limited by wheel-rail support and power supply by pantograph. The high-speed maglev train levitates the train by electromagnetic force and cancels the wheel and rail. The long stator synchronous linear motor is used to supply power to the ground coil, which cancels the pantograph, realizes the ground flight without touching the ground and using fuel, and overcomes the main difficulties of the traditional wheel-rail railway. Because it is hung on the track and equipped with facilities according to the fire protection standards of the aircraft, it is stable and comfortable to ride and has a very high safety.

Some people worry that in case of power failure, the train will fall immediately. In fact, this problem has long been considered in the design. The maglev train is equipped with standby power supply. In case of power failure, the system will automatically switch to the standby power supply, which can continue to maintain the train running for a period of time. In this process, the train speed will gradually slow down, the height from the ground will gradually decrease, and finally land smoothly. There will be no sudden landing of high-speed trains after power failure.

German and Japanese pay attention to China's magnetic levitation technology.

The news that China will build a maglev train line from Shanghai to Hangzhou, and plans to officially start construction at the end of this year has attracted foreign media reports. Among them, Germans and Japanese are very concerned about China maglev. When China announced that this maglev line would first adopt China's independent technology, the German reaction quickly changed from shock and loss to doubt, and then began to face up to reality and seek cooperation, while Japan was more concerned with the comparison and reflection of its own maglev technology research and development path.

It is reported that the Shanghai-Hangzhou maglev line will lay a dedicated track with a total length of 175 km between Shanghai and Hangzhou, and the maximum speed of the train can reach 450 km/h. Considering the noise and other problems, the running speed in the urban area will be controlled at 200 kilometers.

According to the plan, this maglev line will be put into operation before the 20 10 Shanghai World Expo. According to experts' estimation, the project cost of maglev line from Shanghai to Hangzhou is 35 billion yuan.

In 2003, the world's first maglev train was put into commercial operation in China and Shanghai. In order to gain a bigger market, ThyssenKrupp and Siemens, who have been negotiating with China, certainly don't want China to develop its own maglev train.

Last month, German media reported that China Chengdu Aircraft Industry Group is developing its own maglev train, which will be tested in Shanghai in July this year. The design speed of the new train is faster than that of German maglev, but German technology is not used. The development project of Dolphin high-speed maglev vehicle, which belongs to the National 863 Program, was put into production in Chengdu last September. In July this year, "Dolphin" will be tested on the track of Shanghai Tongji University 1.7 km.

Many German media reported that China had developed its own maglev train. Although Engineer Zheng, the project leader of Chengdu Aircraft Industry Group in China, said that China's maglev train technology used some aerospace technologies that Germany did not have, and was more advanced than Germany in lightweight design, China's viewpoint of copying German maglev technology began to appear in German newspapers. Among them, Bavarian Governor Stauber is the most representative. He claimed that the incident "smells like technical theft".

However, Peter, director of the German Institute of Railway Technology in Berlin? Nicole said that the possibility that China copied the protected German magnetic levitation technology on a large scale could be ruled out. Feng Bile, former president of Siemens, said that Siemens had long known that China was engaged in magnetic levitation research at Tongji University. He said that Germans should know that even if they develop their own magnetic levitation technology, they will be further developed elsewhere if they don't apply it. Peter. Nico expressed the hope that Germany and China will continue to develop magnetic levitation technology in the future.

Frankfurter allgemeine zeitung commented that, up to now, "the maglev train in Shanghai is more of a tourist attraction than an economically and technically meaningful means of transportation". But the Shanghai-Hangzhou maglev line will change this.

According to Japanese media analysis, although one of the bottlenecks in China's social development is the underdeveloped transportation network, the construction of Shanghai-Hangzhou maglev line and Beijing-Shanghai high-speed railway is stepping up, and a number of large-scale strategic projects are becoming a reality under the leadership of the government. In contrast, Tokyo has spent decades without even building a high-speed ring road, which shows that the Japanese government lacks strategic vision.

Nikkei BP's report entitled "Enlightenment of Shanghai Maglev Train to Japan's Future" compares Japan's maglev development plan. It is reported that superconducting has been chosen as the magnetic levitation method in the development of Japanese maglev trains since 1970s. Because Japan is a country with frequent earthquakes, the suspension distance can reach more than 100 mm by using high-power superconducting magnets. However, the levitation distance of Shanghai maglev train in normal guidance mode is about 8 mm, and another advantage of superconducting mode is that it can drive magnets in constant current mode, so it can not provide levitation power to the car body, and the car body is light and simple.

However, for the practical application of superconducting maglev train, there are huge obstacles in both quantity and quality. After solving many problems one by one, and carrying out a stable driving experiment at a speed of more than 500 kilometers per hour on Yamanashi Experimental Line, the Technical Evaluation Committee of Japan's Ministry of Land, Infrastructure, Transport and Tourism finally made an evaluation that "the practical basic technology has been established" in March last year.