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The permanent magnet traction system
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The permanent magnet traction system

Author: Site Editor     Publish Time: 2020-12-17      Origin: Site

Permanent magnet technology is an application technology produced by the development of permanent magnet materials. Its applications ranging from TV remote controls to high-speed trains. Permanent magnets are magnets that can maintain magnetism, such as natural magnets and artificial magnets processed by people. Natural magnets are made from natural minerals that are affected by the earth's internal magnetic field and become a natural magnet. However, natural magnets are limited.

Natural magnet

We apply more artificial permanent magnets. It is made of some metal alloy materials after proper treatment so that it can have long-term magnetism. If there is a magnetic field around the magnet, the iron will be magnetized when it approaches, and the magnetized iron block and the magnet can attract each other. This is because the iron block is in the magnetic field generated by the magnet. When the iron block leaves this magnetic field, the so-called magnetism of the iron block also disappears. Artificial magnets are usually made of iron powder or some alloy. Its magnetism is much stronger than natural magnets. Especially the magnetic properties of rare-earth alloys. Not only extremely strong but also much more stable.

Artificial permanent magnet

Principle of the permanent magnet motor

In 1820, Danish scientist Hans Christian Ørsted discovered the principle of electromagnets. But magnets can generate magnetic force through electric current. It is not a permanent magnet. Because once the power is cut off, its magnetism will disappear. Once it is energized, it will easily suck up the iron. Turn off the power and the magnetic field will disappear. 

When two electromagnets that are energized meet, they can attract each other. The rotation of one electromagnet will drive the other electromagnet to rotate. This is how traditional motor works. The rotating electromagnet is equivalent to the stator in the motor. The one that is taken to rotate is equivalent to the rotor. After the stator is energized, a magnetic field is generated to drive the rotor to move. This movement is the process of converting electrical energy into mechanical energy. With the development of technology, people have applied motors to rockets, satellites, high-speed railways, ships, and automobiles. Almost everywhere we can think of.

The magnetism of the electromagnet needs to be maintained by turning on and off the current. So is there a more energy-saving and environmentally friendly technology to play the huge role of magnetism? Yes, this is permanent magnet technology. If one of the magnets in the traditional motor is replaced by a permanent magnet, after the electromagnet is switched on, they can attract each other. The permanent magnet has its own magnetism, and the permanent magnet is not energized at this time. In the rotating magnetic field, it is pulled and rotated by the electromagnet, and the effect of converting electrical energy into kinetic energy can still be achieved. The energy-saving effect is clear at a glance. This is the basic principle of the permanent magnet motor.

Permanent magnet motor

The huge energy of permanent magnets

On the road, we often see a car being dragged forward by another car. At this time, the pulling force of the steel wire rope needs to be greater than the gravity of the broken down car behind multiplied by the coefficient of friction. In the experiment of the magnetic pull effect of the rare earth permanent magnet, there is a steel wire rope at the tail of the pickup truck and the head of the minibus. Two steel wire ropes are connected with iron pieces at both ends. The two iron sheets are connected by a rare earth permanent magnet. When the pickup truck started slowly, the two steel wire ropes connected by permanent magnets were tightened and pulled the minibus forward. With the help of rare earth permanent magnets, the pickup truck drove a minibus whose weight and volume far exceeded it.

Tensile test

This rare earth permanent magnet with strong magnetism is about 3.6cm in diameter, 3.2cm in height, and weighs about 250g. The minibus driven by the traction it conducts weighs about 4 tons. It is conceivable that a small permanent magnet has huge energy.

Rare earth permanent magnet

So the power of permanent magnets is so huge, will we be affected by the radiation of household appliances or transportation equipment equipped with permanent magnet motors?

Permanent magnet motors generate magnetic fields from rare earth permanent magnet materials, which have a strong magnetic field. But after the permanent magnet is installed in the motor, the ferromagnetic material around the motor has a shielding effect on the magnetic field. The strength of the externally leaked magnetic field is similar to that of the earth's magnetic field. Will not adversely affect the human body. So there is no radiation.

Rare earth permanent magnets are not only safe but also powerful. If the rare earth permanent magnet motor can be applied to rail transit, it can give full play to its advantages.

The permanent magnet traction system

Permanent magnet technology is not a new technology. It has existed for a long time and has been applied to some household appliances with relatively small power. From the perspective of scientific principles, permanent magnet technology can have a wider range of applications. But this depends on the improvement of materials and technology.

Permanent magnet traction system for rail transit

In 2011, the permanent magnet traction system was successfully installed on the Shenyang Metro Line 2 in China. The first application in the field of rail transit is realized. The power of the permanent magnet traction system used in the subway is 190 kilowatts. The test results show that the energy-saving effect is increased by 35%, and the permanent magnet traction system is therefore called an energy-saving artifact. By 2020, about 100 urban rail transit lines are planned to be built. If the new line adopts a permanent magnet traction system, the expected output value will reach 10 billion yuan. The country’s annual energy consumption for new line operations will save 240 million yuan.

Rail transit subway

In 2014, a permanent magnet traction system with a power of 690 kilowatts was installed on the high-speed rail. The permanent magnet traction system with completely independent intellectual property rights, like a thumping young heart, sends the strongest sound to the world.

Permanent magnet motors for new energy vehicles

Take the permanent magnet motor of a new energy vehicle as an example to illustrate the importance of materials and structure. In the absence of oil resources and serious environmental pollution. New energy vehicles are the most reliable and sustainable technological route to ensure the most reliable vehicle power. For new energy vehicles, the core of the drive system is the drive motor. Because the permanent magnet motor has a series of advantages such as energy-saving, environmental protection, and stable operation. Permanent magnet motors are the most ideal choice for new energy vehicles. The renewal of power energy provides the possibility for new energy vehicles to move from life to the field. The decisive role here is the heart of new energy vehicles, rare earth permanent magnet motors.

Rare earth permanent magnet motor

It is a long process to use rare earth disassembly in permanent magnet motors. The world's first electric motor appeared in the 1820s. The rotor part of this motor is a permanent magnet, but the permanent magnet material used at that time is natural magnetite. Its magnetic energy density is very low, and the motor made with it is bulky. Was eliminated soon. 

With the development of technology, there have been many options for dismantling permanent magnets. After the test of practice, the members of the rare earth family stand out. Permanent magnets made of rare earth disassembled materials have become the first choice for permanent magnet motors with stable and superior performance. Rare earth permanent magnets are made of rare earth raw materials and other metals through complex processes such as melting, cooling, crushing, and sintering to form a blank. 



Then it is magnetized by a strong current to form a permanent magnet. This process of magnetization is called magnetization. The permanent magnet after magnetization can establish a strong permanent magnetic field.


Currently, rare earth permanent magnets widely used mainly include neodymium iron boron and samarium cobalt permanent magnets. Permanent magnet motors are not only energy-saving but also simple in structure and reliable in operation. It can also be small in size and light in weight. There are greater possibilities in the application. While the market is familiar with new energy vehicles using asynchronous motors, we have already used rare earth permanent magnet motors.

The shopping price of household products or new energy vehicles are driven by permanent magnet technology is slightly higher than that of common products. However, it has a longer service life, low consumption, energy-saving, and a higher cost performance than products equipped with ordinary motors. The successful application of rare earth permanent magnet materials in household appliances and new energy vehicles has laid a solid foundation for the technological development of permanent magnet traction systems. It also provides a technical reference for the application of permanent magnet technology to rail transit.

Will the magnetism of the permanent magnet in the permanent magnet motor be gradually consumed?

The motor is a conversion device of electrical and mechanical energy, and the magnetic field generated by the permanent magnet is the medium for energy conversion. During the operation of the motor, the magnetic field will not be consumed. Just like a boat walking on the water, the water will not be consumed.

Can the permanent magnets in permanent magnet motors be able to withstand high temperatures?

In order to avoid water, dust, iron filings, etc. from corroding the permanent magnets inside the motor, the motor adopts a fully enclosed structure. Because the power of the permanent magnet motor is too large, the heat is too high. Permanent magnet materials may have serious risks of irreversible loss of magnetism under conditions such as high-temperature vibration. If the train loses its magnetism during high-speed operation, the consequences are hard to imagine. Therefore, permanent magnets used in high-speed rail traction systems must have high-temperature resistance characteristics.

High-speed new energy vehicles have been in a state of high-speed operation. The speed of its permanent magnet synchronous motor can even reach 12,000 rpm, which requires the high-temperature adaptability of the vehicle motor. It is the optimization of rare earth permanent magnet materials that makes the motor have good heat resistance. The same high-performance rare earth materials also provide the necessary conditions for permanent magnet traction systems to be applied to high-speed rail. Permanent magnets that can withstand high and low temperatures are also the top priority.

High-speed rail test box freezing test

In order to prevent the permanent magnets from losing their magnetism, the research team adopted the method of self-developed permanent magnet built-in magnetic circuit structure. Effectively control the heating of the motor. The temperature measurement range of the high-speed rail test box is from minus 40 degrees Celsius to 40 degrees Celsius. The tested high-speed rail and permanent magnet traction system engines mean that they have passed through the severe cold and heat throughout the year. The rigorously tested high-speed rail with a permanent magnet traction system drives the development of high-speed rail in the new era.

permanent magnet traction system drives

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