This section provides overview, applications, and principles of linear motors. Also, please take a look at the list of 9 linear motor manufacturers and their company rankings.
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A linear motor is a motor that uses the attraction and repulsion of magnets or Lorentz force to generate propulsive force.
While ordinary motors generate rotational motion, linear motors drive linear motion. In other words, the structure is such that the magnets move along a rail.
While driving linear motion with conventional motors requires a combination of various motors and parts, linear motors make it easy to drive linear motion without such complicated mechanisms.
The most famous application of linear motors is in linear motors cars, including the linear bullet train.
Cars on the Oedo Line of Tokyo's Toei Subway and the Kaigan Line of Kobe Municipal Subway are driven by linear motors.
Since linear motors cars do not have wheels and the car body floats on rails due to repulsion of magnets, they can move at high speeds with very little loss of driving force due to friction.
Linear motors are also increasingly being used in other industrial equipment drive units.
Linear motors are driven by the attraction and repulsion of magnets.
In this respect, they are similar to conventional motors. However, linear motors have a structure similar to a conventional motor that has been cut open in order to generate a linear motion.
Therefore, it is different in principle from conventional motors that have mechanical shafts and are driven by torque. As with conventional motors, there are two types: the induction type, which is driven by Lorentz force due to electromagnetic induction, and the synchronous type, which uses repulsion and attraction of magnetic poles. In the induction type, an electromagnet is placed on a magnet with NS-SN aligned magnetic poles and driven by an electric current.
On the other hand, in the synchronous type, the magnetic poles of the fixed magnets are changed in accordance with the movement of the movable electromagnets in order to move the movable electromagnets on the linearly aligned fixed magnets.
In general, the synchronous type is used in linear motors cars to reduce power consumption, while the induction type is often used in shaft motors for industrial machinery to ensure strict control.
In particular, linear motors cars use superconducting magnets in the electromagnets on the car body side to minimize power supply.
A typical application of linear motors is linear motors cars. Although the advantages of linear motors in terms of higher speeds have been widely highlighted, there was a time when market expansion was slow due to many design and control issues. However, recent improvements in linear motor performance and control technology have led to reconsidering how linear motors can be used.
The advantages of linear motors include that they do not require a reduction mechanism and can feed with high precision. They can be used for longer axes, and multiple motors can be arranged to operate simultaneously.
Demerits include difficulty controlling disturbance effects, difficulty obtaining high thrust, and difficulty in inspection and maintenance.
In recent years, various technological improvements have reduced the disadvantages of linear motors, and efforts are underway to further utilize their features and advantages.
Under these circumstances, attention has shifted from "higher speeds" to "higher precision," and the use of linear motors in grinding machines, lathes, and other machine tools is progressing. Furthermore, since linear motors are driven by electric energy, from the viewpoint of environmental conservation, future possibilities include their use in large hydraulic machines.
Superconductive magnets are used to drive linear motors cars, utilizing the phenomenon of superconductivity, in which electrical resistance becomes zero at a low temperature of 4K (-269°C), thereby generating a strong magnetic field with no loss of electrical energy.
In order to maintain a constant state of superconductivity, a cooling system must be installed, and conventionally, liquid helium was used for cooling. Liquid helium is expensive and has the disadvantage of requiring large equipment to ensure safety.
In recent years, it has become possible to directly cool superconducting magnets without using liquid helium by changing the materials used for the coils that make up the magnets. The material used is bismuth-based copper oxide, and the temperature at which superconductivity is achieved is higher than before, at 20K (-253°C), making it possible to cool the magnet, which is called a high-temperature superconducting magnet.
The device used to cool the high-temperature superconducting magnet directly cools the material using adiabatic expansion, and technological improvements in the cooler itself have made it lighter and more compact.
Further progress in the practical application of high-temperature superconducting magnets, including the cooling system, will greatly contribute to energy conservation, cost reduction, and stability improvement.
*Including some distributors, etc.
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