The maglev train is guided by electromagnetic force. According to the constant magnetic attraction and superconducting magnetic repulsion, it is briefly described as follows.
Similar to the suspension system, the constant magnetic gravity guidance system is to install a group of electromagnets specially used for guidance on the side of the vehicle. There is a certain gap between the car body and the side of the guide rail.
When the vehicle deviates from left to right, the guide electromagnet on the vehicle interacts with the side of the guide rail to restore the vehicle to its normal position. The control system maintains this lateral gap by controlling the current in the guide magnet, thus controlling the running direction of the train.
Superconducting magnetic repulsion guidance system can be constructed in the following three ways:
(1) Install a mechanical guide device on the vehicle to realize train guidance. This device usually uses the side guide auxiliary wheel on the vehicle to make it interact with the side of the guide rail (rolling friction) to generate restoring force, which is balanced with the lateral force generated when the train runs along the curve, so that the train runs along the center line of the guide rail.
(2) A special guiding superconducting magnet is installed on the vehicle to generate magnetic repulsion with the grounding coil and metal belt on the side of the guide rail, which is balanced with the lateral force of the train to keep the train running in the right direction. This guidance mode avoids mechanical friction, and the train can keep a certain lateral clearance as long as the current in the lateral ground guidance coil is controlled. ?
(3) The "zero flux" guidance system guided by magnetic force lays a closed coil in the shape of "8". When the superconducting magnet installed on the train is located on the symmetrical center line of the coil, the magnetic field in the coil is zero; When the train moves laterally, the magnetic field in the "8" coil is zero, which produces a reaction force to balance the lateral force of the train and make the train return to the position of the center line of the line.
2. Propulsion mode
The key technology of the propulsion system of maglev train is to expand the rotating motor into a linear motor. Its basic composition and principle of action are similar to those of ordinary rotating machines. After deployment, its transmission mode will change from rotary motion to linear motion.
Constant permeability magnetic levitation adopts short stator asynchronous linear motor. Install the three-phase armature winding on the vehicle and the induction rail on the track. Vehicle-mounted power supply is adopted. This mode has the advantages of simple structure, convenient maintenance and low cost, and is suitable for medium and low-speed urban traffic and suburban traffic as well as short-distance travel route system. The main disadvantage is low power, which is not conducive to high-speed operation.
Among them, TR bullet train, Transrapid 06 maglev train imported from Shanghai and HSST maglev train in Japan all adopt this form. Superconducting magnetic repulsion magnetic levitation adopts long stator synchronous linear motor. Its superconducting electromagnet is installed on the vehicle, and the passive closed coil or non-magnetic metal plate is arranged along the track.
Using superconducting electromagnetic coil as magnetic suspension device provides convenient conditions for the excitation coil of linear synchronous motor to be in superconducting state. They can be stored in the same cooling system or suspended, guided and propelled by the same coil at the same time.
The traction system of high-speed long stator synchronous linear motor is relatively complex. In the ground traction system, the power supply of one section (about 30km long) is divided into multiple sections (about 300- 1000 m), each section only supplies power when the train passes, and the switching of each section is completed by a contact vacuum switch.
In order to prevent the train from section impact, two sets of inverters are needed for alternating power supply, which are characterized by high power, high voltage and high current. The advantages of ground power supply include high power of rail motor, simplified design and light weight of vehicles. Suitable for high-speed and ultra-high-speed maglev railways. Japan and Canada decided to develop this magnetic levitation system.
4. Train kinetic energy
"Normal-oriented" maglev train, the working principle of track and motor is exactly the same.
Just arrange the "rotor" of the motor on the train and lay the "stator" of the motor on the track. Through the interaction between "rotor" and "stator", electric energy is converted into positive kinetic energy.
We know that when the "stator" of the motor is electrified, the "rotor" can be driven to rotate through the action of current on the magnetic field. But the power consumption is huge, just like a motor covering the track. When electric energy is transmitted to the "stator" of the track, the train is driven to move linearly like the "rotor" of the motor through the action of current on the magnetic field.
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Advantages and disadvantages of magnetic levitation technology
1, advantages
Maglev train has many advantages: the train is suspended above the rail, and the rail is not in contact with the vehicle, which not only runs very fast, but also exceeds 500 km/h; No noise and harmful waste gas, which is beneficial to environmental protection. Because there is no need for wheel and wheel-rail friction, the maintenance workload and operating cost are reduced.
It is an ideal super express train in 2 1 century, and all countries in the world attach great importance to the development of maglev train. By 20 12, China, Japan, Germany, Britain, the United States and other countries are actively studying this kind of car. The Japanese superconducting maglev train has passed the on-orbit test and is about to enter the practical stage, running at a speed of more than 300 kilometers per hour.
The maglev train keeps a certain gap (generally1-10 cm) with the track during operation, so it runs safely, smoothly and comfortably, without noise, and can realize full-automatic operation.
The service life of maglev train can reach 35 years, while that of ordinary wheel-rail train is only 20-25 years. The service life of maglev train track is 80 years, while that of ordinary track is only 60 years. At present, the highest speed reached by Japanese L0 maglev train 20 15 is 603 km/h.
According to German scientists' prediction, the speed of maglev train will reach 1000 km/h in 20 years after adopting new technology. At present, the maximum speed of wheel-rail trains in China is 496 km/h (the maximum speed of TGV electric trains in France reached 574.8 km/h in the test in 2007).
2. Deficiencies
It is said that it is very dangerous for vehicles on land to have no wheels. To overcome the large inertia, only through the braking force of wheels and tracks can it be overcome. Maglev trains have no wheels. It is very dangerous to rely on sliding friction if there is a sudden power failure.
For magnetic levitation, in case of sudden power failure, it is precisely the tragedy that magnetic levitation will be more dangerous than wheel-rail sliding friction braking, resulting in car crash and death. It is precisely this feature that there are no cases of construction abroad.
In addition, the maglev train is elevated, and it is difficult to rescue at a height of 5 meters when an accident occurs. Without wheels, it is difficult to drag it out of the scene of the accident. If there is a power outage in the section, it is difficult for other vehicles and cranes to get close. However, compared with other wheel-rail railways, high-speed rail, subway and light rail are also elevated.
In 2006, a German maglev control train collided with a maintenance vehicle during its trial operation. It is reported that there were 29 people on board, 23 people died on the spot, 25 people actually died and 4 people were seriously injured. This shows that the braking ability of maglev train in emergency is not reliable, which is not as good as that of wheel-rail train. It shows that the braking ability and safety of maglev train are far worse than that of wheel-rail train in emergency (wheel-rail safety is several times higher).
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