Application of NdFeB permanent magnet in magnetic suspension field

What is magnetic levitation?

Magnetic levitation is a technology that uses a magnetic field to levitate objects in the air. It is a technology that uses magnetic force to overcome gravity to levitate objects. It is also known as magnetic levitation technology. Magnetic levitation is a frictionless method of lifting objects. It is also more efficient because less energy is used to overcome friction.
All it requires for magnetic levitation is a strong magnetic field. Permanent magnets are needed to provide this magnetic field. The most used permanent magnets in the field of magnetic levitation are neodymium iron boron magnets.

The working principle of magnetic levitation

There are three basic principles of magnetic levitation:

• 1. When the magnetic field near a metal changes, the electrons on the metal move and a current is generated.
• 2. The magnetic effect of the current. When an electric current flows in a wire or piece of metal, a magnetic field is created. An energized coil becomes a magnet.
• 3. Magnets will act on each other, repelling each other with the same polarity and attracting each other with different polarity.

Advantages and disadvantages of magnetic levitation

Advantages of magnetic levitation
Magnetic levitation trains have many advantages: the trains run in levitation above the railroad tracks, and the rails do not come into contact with the vehicles, so not only do they run very fast, which can exceed 500 km/h,; they are noiseless and do not emit harmful exhaust gases, which is conducive to environmental protection. As there is no need for wheels, there is no wheel pair wear caused by wheel-rail friction, reducing maintenance workload and operating costs.
It is the ideal super special express train in the 21st century, and countries around the world attach great importance to the development of maglev trains. By 2012, China and countries such as Japan, Germany, the United Kingdom and the United States are actively researching this type of vehicle. Japan’s superconducting maglev trains have been tested in orbit and are about to enter the practical stage, running at speeds of more than 300 km/h.
Maglev trains run with a certain gap (generally 1-10cm) with the track, so the operation is safe, smooth and comfortable, no noise, and can achieve fully automated operation. The service life of maglev trains can reach 35 years, while ordinary wheel track trains only have 20-25 years. The life span of Maglev train tracks is 80 years, while ordinary tracks are only 60 years. The highest speed is 603 km/h reached by the Japanese L0 maglev train in 2015. According to German scientists, it is predicted that by 20 years, maglev trains will reach 1000 km/h with the new technology. And the current maximum speed of wheeled trains operating in China is 496 km/h (the highest speed of French TGV electric trains has reached 574.8 km/h in a test in 2007).
Disadvantages of Maglev
It is claimed that transportation on land without wheels is dangerous. The only way to overcome the great inertia is through the braking force of the wheels against the track. Maglev trains do not have wheels, and it is dangerous to rely on sliding friction if there is a sudden power failure. For the magnetic levitation, when encountering a sudden power failure, take the mechanical arm locking track forced parking, which is exactly the magnetic levitation compared to the wheel track sliding friction braking method will be more dangerous, will lead to car destruction tragedy, no case abroad to build exactly this feature.
In addition, maglev trains and elevated, in the event of an accident at a height of 5 meters rescue is very difficult, no wheels, dragging out the accident scene difficult; if the district power outage, other vehicles, cranes are also difficult to approach. But compared to other wheeled railroads, whether high-speed rail, subway, or light rail, is also the same elevated.
In 2006, the German maglev control train collided with a maintenance car during a trial run, and the report said that there were 29 people on board, 23 died on the spot, 25 actually died and 4 were seriously injured. This shows that the braking ability of maglev trains in sudden situations is not reliable and is not as good as that of wheel rail trains. It shows that the braking ability of maglev trains in sudden situations is far less than that of wheel-track trains, and the safety is not as high as that of wheel-track trains (wheel-track safety is tens of times higher).

Application of magnetic levitation

1. Magnetic levitation train
Magnetic levitation train is a modern high-tech rail transportation, it achieves contactless levitation and guidance between the train and the track through electromagnetic force, and then uses the electromagnetic force generated by the linear motor to traction the train operation, its main technical system principle includes three parts:

• ① levitation system;
• ② propulsion system;
• ③ guidance system.

The levitation system is through the magnet “same name magnetic repulsion, different name magnetic attraction” principle to achieve the effect of train levitation, the propulsion system is through the permanent magnet synchronous traction motor to make the train maintain linear motion. So what materials are these magnets made of? Among them, the most important one is the rare earth permanent magnet material.
Rare-earth permanent magnet material is a magnetic material made of rare-earth metal elements (samarium, neodymium mixed rare-earth metals) and transition group metals (such as cobalt, iron, etc.) composed of alloy, pressed and sintered by powder metallurgy method, and magnetized by magnetic field, mainly divided into rare-earth cobalt-based permanent magnet material and rare-earth iron-based permanent magnet material. They both have the following characteristics.

• (1) High magnetic properties, such as high magnetic energy product.
• (2) Linear demagnetization characteristics: their demagnetization curves are basically straight lines, the recovery line coincides with the demagnetization curve, and the reversible permeability is close to 1.0.
• (3) High temperature resistance: the Curie temperature of sintered cobalt-based rare earth permanent magnets can reach 850 degrees Celsius, so they can be adapted to work in high temperature environments.
• (4) Better temperature stability.

Because of its excellent permanent magnet characteristics, it is used in many applications in maglev trains. Permanent magnet synchronous traction motor, which is the propulsion system of maglev train, often uses samarium cobalt permanent magnets or neodymium iron boron permanent magnets.
2. Magnetic levitation household ornaments

Magnetic levitation globe
Currently on the market, there are two kinds of upper levitation system and lower levitation system.
The lower levitation system has a permanent magnet fixed at the bottom of the bracket, and a circular plastic frame above the bracket, with a metal coil electromagnet inside the frame. The inner wall of the globe also has magnets, and the electromagnet above and the permanent magnet at the base repel each other, and this repulsive force is used to levitate the globe. In order to make the levitation smooth, there is also a detector inside the coil above the stand, which is specially designed to detect the magnetic field changes at the bottom and generate a compensating current to adjust the electromagnetic strength and make the globe levitate smoothly. In stable levitation, the globe can continue to rotate without stopping with a simple turn.
The top of the bracket of the upper levitation system has permanent magnets, and the lower part puts electromagnets, which produce the attraction, and is used to levitate the globe by gravity.
3. Magnetic levitation ornament series.
Now there are many on the market, such as magnetic levitation photo frame, magnetic levitation wine display stand, magnetic levitation electronic cigarette display stand, magnetic levitation tablet display stand, magnetic levitation cell phone display, magnetic levitation mannequin, and so on.
4. Magnetic levitation bearing.
Magnetic levitation bearing, is the use of magnetic force to levitate the rotor, there is no mechanical contact between the rotor and the stator. The weight of the rotor is supported by magnetic force, and the whole rotor is suspended.
5. Magnetic levitation motor
DC magnetic levitation motor is also called magnetic levitation motor, magnetic motor, bearingless motor, which is a new structure of motor. Its principle is: the rotor is embedded with permanent magnets, and the stator is wound with coils to make a multi-pole electromagnetic body to produce a rotating magnetic field, using the same magnetic repulsion principle, the rotor can be repelled by the stator and rotate, not only that, the rotor can also be suspended and rotate.
6. Magnetic levitation doors and windows
Although the magnetic levitation sliding door and magnetic levitation train principle, but it does not really levitate above the track (to achieve the cost is too expensive), is still through the pulley on the track movement.
Source: China Permanent Magnet Manufacturer – www.rizinia.com