Principle Of Linear Motor For Maglev Train


A linear motor is primarily a transmission that convert […]

A linear motor is primarily a transmission that converts electrical energy directly into linear motion mechanical energy without the need for any intermediate conversion mechanism. It is a new technology with new principles and new theories in the field of electrical engineering in the second half of the 20th century. Its special advantages have attracted more and more attention.

The structure of the linear motor can be made into various types such as flat type, cylindrical type, or disk type as needed, and it can be operated by various power sources such as an AC power source, a DC power source, or a pulse power source. The linear motor can pull a helicopter weighing several thousand kilograms to a speed of several hundred kilometers per hour in a matter of seconds, and it can reach tens of thousands of kilometers per hour when it is running in a vacuum. In the military, people use it to make various electromagnetic guns and try to use it for missiles and rocket launches. In the industrial field, linear motors are used to produce conveyor lines, as well as various mechanical devices for lateral or vertical movement. In addition to the characteristics of high speed and large thrust, the linear motor has another feature of low speed and fineness. For example, a stepping linear motor is used to achieve an accuracy of 1 μm, so the linear motor is applied to many Precision instruments and equipment, such as computer head drive, camera shutter, automatic plotter, medical equipment, aerospace equipment, various automated equipment and so on. In addition, linear motors are used in a variety of civil devices, such as doors, windows, tables, chairs, door locks, opening and closing of electric curtains, especially in the transportation industry. People use linear motors to make maglev trains with speeds of up to 500km per hour.

The    Electric Motor Manufacturer   stated that the key technology of the maglev train propulsion system is to expand the rotating electric machine into a linear motor. Its basic structure and working principle are similar to those of ordinary rotating electric machines. After unfolding, its transmission mode changes from rotary motion to linear motion. The normally-guided magnetic suspension uses a short stator asynchronous linear motor. A three-phase armature winding is mounted on the vehicle, and an inductive rail is mounted on the rail. Use the car power supply. This method is simple in structure, easy to maintain, low in cost, suitable for medium and low speed urban transportation and suburban transportation, and as a short-distance travel line system; the main disadvantage is that the power is low, which is not conducive to high-speed operation. The TR-type fast-moving train and the Transrapid 06 maglev train introduced in Shanghai and the HSST-type maglev train in Japan all adopt this form. The superconducting magnetic repulsion magnetic levitation uses a long stator synchronous linear motor. Its superconducting magnet is mounted on the vehicle with passive closed coils or non-magnetic metal plates placed along the track. The use of a superconducting magnetic coil as a magnetic levitation device provides a convenient condition for the excitation coil of a linear synchronous motor to be in a superconducting state. They can coexist in the same cooling system, or the same coil can simultaneously suspend, direct and propel. The structure of the high speed long stator synchronous linear motor traction system is relatively complicated. In the ground traction system, the interval of power supply (length about 30km) is divided into many sections (about 300-1000 m). Each section only supplies power when the train passes, and each section is switched by the contact vacuum switch. In order to make the train not impulsive between the segments, two sets of inverters are required to be supplied in turn, which are characterized by high power, high voltage and large current. The advantage of power on the ground is the power of the rail motor and the design of the vehicle is simplified and light. Suitable for high speed and ultra high speed magnetic levitation railways. Japan and Canada decided to develop this magnetic levitation system.


The drive of the maglev train uses the principle of a synchronous linear motor. The lower part of the vehicle supports the electromagnet coil as the excitation coil of the synchronous linear motor. The three-phase moving magnetic field drive winding inside the ground track acts as an armature, which is like the long stator winding of the synchronous linear motor. It can be known from the working principle of the electric motor that when the armature coil as the stator is energized, the rotor of the motor is driven to rotate due to electromagnetic induction. Similarly, when a substation arranged along the line provides three-phase frequency modulated power to the drive winding inside the track, the electromagnetic induction carrying system is pushed along with the train like a "rotor" of the motor for linear motion. Thus, in the suspended state, the train can completely achieve non-contact traction and braking.

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