Analysis and introduction of the principle of maglev technology and the working principle of maglev train

What is a maglev train?

Maglev trains are a new type of transportation consisting of contactless electromagnetic suspension, guidance and drive systems. Maglev trains are divided into two categories: superconducting and conventional. Simply put, in terms of internal technology, the difference between the two systems is whether they use magnetic repulsion or magnetic attraction. In terms of external appearance, there is a difference in speed between the two: the superconducting maglev train can reach a maximum speed of more than 500 kilometers per hour (the maximum speed of high-speed wheel-rail trains is generally 300-350 kilometers per hour), which can compete with aviation within a distance of 1,000 to 1,500 kilometers; while the conventional maglev train has a speed of 400 to 500 kilometers per hour, and its medium and low speeds are more suitable for long-distance rapid transportation between cities.

The Shanghai Maglev Train is a "conventional magnetic attraction type" (abbreviated as "conventional magnetic attraction type") maglev train.

Technical foundation of maglev train

The maglev train is mainly composed of three parts: suspension system, propulsion system and guidance system, as shown in the figure. Although it is possible to use a propulsion system that has nothing to do with magnetism, in most current designs, the functions of these three parts are all completed by magnetism.

How Maglev Trains Work

The maglev train uses the principle of "like repels like and opposites attract" to give magnets the ability to resist gravity, allowing the car body to completely leave the track, float about 1 cm above the track, and travel in the air, creating the miracle of nearly "zero altitude" space flight.

How does a maglev train work?

The maglev train is a high-tech means of transportation that utilizes the attraction and repulsion of magnetic poles.

The repulsive force keeps the train suspended, and the attractive force makes the train move.

The maglev train is equipped with superconducting magnets on the carriages and coils at the bottom of the railway. After power is turned on, the polarity of the magnetic field generated by the ground coils is always the same as the polarity of the electromagnets in the carriages, and the two "repel each other with like charges".

The repulsive force makes the train float. The power of conventional locomotives comes from the locomotive, while the power of maglev trains comes from the track. Coils are installed on both sides of the track. The alternating current turns the coils into electromagnets, which interact with the magnets on the train. When the train is running, the magnet on the front of the train (N pole) is attracted by the electromagnet (S pole) a little ahead on the track, and is repelled by the electromagnet (N pole) a little behind on the track. The result is that the front "pull" and the back "push", making the train move forward.

When the train reaches the position indicated on the diagram, the direction of the current flowing in the coil is reversed. As a result, the original S-pole coil now becomes an N-pole coil, and vice versa.

When the train reaches the position indicated on the diagram, the direction of the current flowing in the coil is reversed. As a result, the original S-pole coil now becomes an N-pole coil, and vice versa.

Linear synchronous motor: Its primary winding is laid along the track, and the secondary winding is installed on the car body. Three-phase alternating current is passed through the primary winding, and a translational magnetic field is generated in the air gap. This magnetic field cuts the secondary conductor, generates electromagnetic induction, and induces a magnetic field. This magnetic field is opposite to the original translational magnetic field, and finally generates electromagnetic thrust between the track and the car body.

Advantages of Maglev Trains

1. It overcomes the main obstacle of increasing the speed of traditional wheel-rail railways and has broad development prospects

2. Maglev trains have high speed

3. Maglev trains have low energy consumption

Current technical issues

Although maglev train technology has many advantages as mentioned above, there are still some shortcomings:

1. Since the magnetic levitation system uses electromagnetic force to complete the suspension, guidance and driving functions, the safety measures of the magnetic levitation after power failure, especially the braking problem after the train power failure, are still issues that need to be solved. Its high-speed stability and reliability still need a long period of operation test.

2. The suspension height of conventional magnetic levitation technology is relatively low, so the requirements for line flatness, roadbed settlement and turnout structure are higher than those for superconducting technology.

3. Due to the eddy current effect, the energy consumption of superconducting magnetic levitation technology is greater than that of conventional magnetic levitation technology, the cooling system is heavy, and the strong magnetic field has an impact on the human body and the environment.