Linear motor, linear motor and magnetic levitation
time£º2014/1/8 click£º11343
Maglev, as we call it, is often associated with linear motor drive.
Maglev transport systems usually use "linear Motors" as propulsion systems, and the characteristics of linear motors are explained first. The general motor is constructed on the middle shaft with a "Rotor" that can rotate, surrounded by a "Stator", and a magnetic field can be generated when the coil is energized. The so-called linear motor is to cut the motor along the axis direction and expand it so that the motor's return is converted into a linear motion, so it is called a linear motor(as shown in Figure 3). The linear motor is divided into a wired induction motor(LIM) and a linear synchronous motor(LSM) due to the different stator and rotor mounting positions: the linear induction motor is equipped with a reaction plate(aluminum plate as a rotor) on the guide rail, and is mounted on the train.
Principle of Composition of Linear Induction Motor[ 1]
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[ 1] And ... 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). Electric suspension(EDS) uses the principle of same-sex rejection. 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 generates 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), Figure 1 shows the combination of an electric suspension system(EDS) and a linear synchronous motor(LSM).
Linear motor