Linear motor and magnetic levitation train
time£º2017/4/7 click£º8782
Linear motor, also known as linear motor, is a kind of traditional rotating motor cut in the direction of the axis, the primary expansion of the rotating motor is used as the stator of the linear motor, and the secondary power is applied to the primary linear motion under the action of electromagnetic force. Become a motor of a linear motor.
Linear motor principle
Maglev, as we call it, is often associated with linear motor drive. Maglev transport systems usually use "linear Motors", that is, linear Motors, as propulsion systems.
The following is the first to understand the principle of the formation of a linear motor:
Set up a moving magnet(as a stator) for three-phase AC power excitation, clamped in two rows on both sides of the aluminum plate(but without contact), the magnetic wire intersects the aluminum plate vertically, and the aluminum plate is induced to generate current, thus generating a driving force. Since the stator of the linear induction motor is installed on the train and is shorter than the guide rail, the linear induction motor is also called "Short stator Motor"; The principle of the linear synchronous motor is to install the superconducting electromagnetic stone on the train(as a rotor), and the track is equipped with a three-phase electric pivot(as a stator), when the coil on the track is supplied with a variable number of cycles. When the three-phase alternating current is used, it can drive the vehicle. Since the speed of the vehicle moves at a synchronous speed proportional to the number of three-phase alternating current weekly waves, it is called a linear synchronous motor, and because the stator of the linear synchronous motor is mounted on the orbit, it is the same length as the orbit. Therefore, a linear synchronous motor is also called a "long-stator motor."
Due to the use of dedicated tracks and the use of steel wheels as support and guidance, the traditional rail transportation system will increase the driving resistance as the speed increases, and the traction force will decrease. When the train travel resistance is greater than the traction, it can no longer accelerate. Therefore, it has not been possible to break through the bottleneck of the theoretical peak speed of 375 kilometers per hour of the ground transportation system. Although the French TGV once set a world record of 515.3 kilometers per hour for traditional rail transport systems, due to the problem of overheating and fatigue in wheel-rail materials, the commercial operating speed of high-speed rail in Germany, France, the West, and Japan today does not exceed 300 kilometers.
Therefore, if you want to further increase the speed of the vehicle, you must abandon the traditional use of wheels and use "magnetic levitation"(`` Maglev ") to float the train away from the lane. To reduce friction and greatly increase the speed of the vehicle. This floating away from the driveway will not cause noise or air pollution, and will increase the efficiency of energy use. In addition, the use of "Linear Motor" can also speed up the maglev transportation system, so the use of linear Motors maglev transportation system came into being.
The so-called maglev transportation system uses the principle of magnetic attraction or rejection to float the train out of the lane. The source of this magnetic force can be divided into "Permanent Magnets" or "Superconducting Magnets"(SCM). The so-called constant conductivity magnet is the general electromagnet, that is, it is magnetic only when it is energized, and the magnetic force disappears when the current is cut off. Because the train is difficult to collect electricity at a higher speed, Therefore, the constant conductivity magnet can only be applied to maglev trains that use the principle of magnetic repulsion and have a relatively slow speed(about 300 kph); As for maglev trains with speeds of up to 500 kph or more(using the principle of magnetic absorption), superconducting magnets that are magnetic(so trains can not collect electricity) can not be used without a single charge.
Because the maglev transportation system uses the principle of magnetic attraction or rejection, it is divided into two types: "Electric Suspension"(EDS) and "Electromagnetic Suspension"(EMS).
Type. Electric suspension(EDS) uses the principle of same-sex exclusion. When the train moves through an external force, the ordinary conductive magnet mounted on the train produces a moving magnetic field, and the coil on the track generates an induced current, which can generate a magnetic field. Since the two magnetic fields have the same direction, the mutual repulsion force between the train and the track is generated, and the mutual repulsion force of the train is lifted and suspended. Since the suspension of the train is achieved by balancing the two magnetic forces, its suspension height can be fixed(about 10 ~ 15mm), and the train therefore has considerable stability. In addition, the train must be started in other ways first, and the magnetic field it carries can generate induced currents and magnetic fields before the vehicle will be suspended; Therefore, the train must be equipped with wheels for "take-off" and "landing". When the speed reaches 40 kph or more, the train begins to suspend(ie, "take off") and the wheels are automatically retracted; Similarly, when the speed is gradually reduced and no longer suspended, the wheel is automatically lowered for taxiing(ie, "landing"). The system that usually uses electric suspension(EDS) can only use "Linear Synchromas Motor(LSM)" as a propulsion system, and its speed is relatively slow(about 300 kph).
Combination of Electric Suspension System(EDS) and Linear Synchronous Motor(LSM)
Electromagnetic suspension(EMS) uses the principle of heterosexual absorption. The sides of the train are surrounded by guide rails(similar to cross-seat monorail systems). The lower part of the train is surrounded by electromagnetic stones. The bottom of the guide rail is equipped with steel plates instead of coils. At this time, the steel plate of the guide rail is on, When the electromagnet of the train is under, when the electromagnet is excited, the magnetic field attraction generated by the electromagnet attracts the train upwards, and the train sinks due to gravity. When the two forces balance, the gap between the train and the guide rail is generated(Gap), and the train is suspended. Its suspension height(about 10 ~ 15mm) varies due to the strength of the magnetic force, so the excitation current of the magnetic field must be closed loop to maintain magnetic stability. In addition, suspension can be generated at the beginning of the train(speed is zero), so the train does not need to install wheels. A system that usually uses electromagnetic suspension(EMS) can use "Linear Induction Motor"(LIM) or linear synchronous motor(LSM) as a propulsion system with a speed of up to 500 kph or more.
In addition to being used for magnetic levitation trains, linear motors are also widely used in other aspects, such as transmission systems, electrical hammers, and electromagnetic mixers. In China, linear motors are also gradually being extended and applied. Although the principle of a linear motor is not complex, it has its own characteristics in design and manufacturing. The product is not as mature as a rotary motor. Therefore, the price of a linear motor has been high, and the linear motor needs further research and improvement.
Linear motor