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Jingzheng Smart takes you to know the extensive application of linear motor in China‘s high-speed railway subway
Linear motor is mainly linear motor, which is a transmission device that directly converts electrical energy into linear motion mechanical energy without any intermediate conversion mechanism. It is a new technology with new principles and theories in the field of electrical engineering in the second half of the 20th century. Its unique advantages have attracted more and more attention.

The structure of linear motor can be made into flat type, cylindrical type or disc type as required, and it can work with AC power, DC power or pulse power. Linear motor can pull a helicopter weighing thousands of kilograms to the speed of hundreds of kilometers per hour in a few seconds. When it runs in vacuum, its speed can reach thousands of kilometers per hour. In military affairs, people use it to make various electromagnetic guns, and try to use it to launch missiles and rockets; In the industrial field, linear motors are used in the production of conveyor lines, as well as some mechanical equipment with various horizontal or vertical movements; In addition to the characteristics of high speed and large thrust, the linear motor also has another characteristics of low speed and precision. For example, the stepping linear motor can achieve a step distance of 1 μ Therefore, linear motor is applied to many precision instruments and equipment, such as magnetic head drive device of computer, shutter of camera, automatic plotter, medical instrument, aerospace instrument, various automatic instruments and equipment, etc. In addition, the linear motor is also used in various civil devices, such as the movement of doors, windows, tables and chairs, the opening and closing of door locks and electric curtains. Especially in the transportation industry, people use the linear motor to make a magnetic levitation train with a speed of more than 500km/h.

Maglev technology is a non-contact technology, which can be used in many applications in rotation and linear motion.

Its application advantages are:

1. Non contact application, no friction, wear, vibration noise greatly reduced, long service life;

2. Special applications, such as vacuum, high temperature, low temperature, steam, organism and other special applications, do not damage the original;

3. For applications requiring control, such as position, over speed, vibration, etc., it is relatively easy to control;

4. It has some special applications, such as the ability to remember, learn and judge, and the ability to monitor, record and diagnose the operation state;

5. Distributed application of controllable force: such as the distribution and control of force at each point of magnetic levitation vehicle and magnetic bearing.

Its future development trends are mainly:

1. In control, the magnetic levitation technology based on DSP has been applied more widely;

2. Permanent magnetic materials and superconducting materials have been further applied in magnetic levitation technology;

3. Multivariable control theory promotes the development of magnetic levitation technology;

4. The development and popularization of computers, VLSI, the development of new materials, the development of space, the advancement and diversification of technology, as well as energy conservation and environmental protection have all put forward requirements for Maglev technology.

Maglev technology has many classifications and corresponding applications according to different combinations of magnets and conductors, and maglev train is just one of them.

The linear motor and magnetic levitation technology constitute the main body of the magnetic levitation train. Different types of linear motors and magnetic levitation technologies constitute different types of magnetic levitation trains.

The magnetic levitation train has changed the way that the traditional rail vehicle is propelled by wheel rail friction. It adopts magnetic levitation car body and linear motor drive technology to make the train float and slide on the track. It is a major breakthrough in the development of transportation technology and is known as an ideal transportation tool in the 21st century. Compared with the existing conventional trains, the outstanding advantages of the maglev train mainly include:

1. High speed, with the speed of more than 500km/h;

2. Safe, without danger of overturning or derailment;

3. No pollution, comfortable ride, no wheel rail contact noise and vibration;

4. It occupies less land, can be elevated and has low requirements for track bearing;

5. Strong adaptability to complex terrain, strong climbing ability and small turning radius;

6. The cost is not high, the overall structure is easy to maintain and energy saving.

Maglev trains can be divided into two categories according to their different types of linear motors and maglev technologies:

1. Normal guide, suction and floating type

This kind of magnetic levitation train is usually called the constant conductor magnetic levitation train, which is generally driven by synchronous or asynchronous linear motors based on the principle of oppositely magnetic poles attracting. Germany is the main representative. The speed can be designed as 100km/h or 500km/h as required. The magnetic levitation height is generally 10mm.

2. Superconducting repulsive floating type

The magnetic levitation train with low temperature superconducting coils, based on the principle of repulsion of the same magnetic poles and generally driven by a synchronous linear motor, is often referred to as the superconducting repulsive magnetic levitation train. Japan is the main representative. Generally, the speed is more than 500 km/h. The magnetic levitation height can reach more than 100mm.

The development direction of maglev train can be divided into three modes: low speed, medium speed and high speed, as shown in Table 1. The reasons for the development of low-speed maglev are: first, the cost of traditional subway systems has risen sharply; The second is the development of power electronic technology and control technology. These two reasons make it competitive with the traditional subway.

The superiority of the maglev train has attracted the attention of many developed countries in the world. Germany, Japan, the United States, Russia, France, the United Kingdom, Canada, South Korea, Switzerland, Sweden and other countries have invested heavily in this research and test. Germany and Japan are the countries with the strongest research and development of maglev trains in the world. They have built several test lines in China. China‘s Shanghai Pudong Line mainly introduces German technology.

Since the 1980s, a few universities and scientific research institutions in China have carried out basic research and experiments on the permanent magnetic levitation train with a small amount of funding from the state. The 4-ton test vehicle developed by Southwest Jiaotong University and the 6-ton test vehicle developed by National Defense University of Science and Technology have been successfully operated. In September 1994, the Chinese Academy of Sciences held a special conference on maglev trains in Xiangshan, Beijing, and proposed to vigorously carry out the research and development of maglev train technology in China. The State Science and Technology Commission has given support to soft topics in this field and included them in the major science and technology plans of the Ninth Five Year Plan and the Tenth Five Year Plan.