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What is a permanent magnet motor?

source:未知   time:2024-10-25 09:13nbsp;  click:

The development history of Wolong Nanyang Explosion Protection permanent magnet motor
The development of permanent magnet motor is closely related to the development of permanent magnet materials. my country is the first country in the world to discover the magnetic properties of permanent magnet materials and apply them in practice. More than 2,000 years ago, my country used the magnetic properties of permanent magnet materials to make compasses, which played a huge role in navigation, military and other fields, and became one of the four great inventions of ancient my country. The world's first motor that appeared in the 1920s was a permanent magnet motor that generated an excitation magnetic field by a permanent magnet. However, the permanent magnet material used at that time was natural magnetite (Fe3O4), which had a very low magnetic energy density. The motor made of it was large in size and was soon replaced by an electric excitation motor. With the rapid development of various motors and the invention of current magnetizers, people have conducted in-depth research on the mechanism, composition and manufacturing technology of permanent magnet materials, and have successively discovered a variety of permanent magnet materials such as carbon steel, tungsten steel, and cobalt steel. In particular, the aluminum-nickel-cobalt permanent magnet that appeared in the 1930s and the ferrite permanent magnet that appeared in the 1950s have greatly improved magnetic properties, and various micro and small motors have used permanent magnet excitation. In the 1960s and 1980s, rare earth cobalt permanent magnets and neodymium iron boron permanent magnets (collectively referred to as rare earth permanent magnets) came out one after another. Their excellent magnetic properties of high remanence density, high coercivity, high magnetic energy product and linear demagnetization curve are particularly suitable for manufacturing motors, thus ushering in a new historical period for the development of permanent magnet motors.
 
Classification of permanent magnet motors
There are many types of permanent magnet motors. According to the function of the motor, it can be roughly divided into two categories: permanent magnet generators and permanent magnet motors.
Permanent magnet motors can be divided into permanent magnet DC motors and permanent magnet AC motors. Permanent magnet AC motors refer to multi-phase synchronous motors with permanent magnet rotors, so they are often called permanent magnet synchronous motors (PMSM).
Permanent magnet DC motors can be divided into permanent magnet brushed DC motors and permanent magnet brushless DC motors (BLDCM) according to whether there is a motor and a commutator.
 
Characteristics and Applications of Permanent Magnet Motors
Compared with traditional electric excitation motors, permanent magnet motors, especially rare earth permanent magnet motors, have the advantages of simple structure, reliable operation, small size, light weight, low loss, high efficiency, and flexible and diverse shapes and sizes of motors. Therefore, the application range is extremely wide, almost covering all fields of aerospace, national defense, industrial and agricultural production and daily life. The following introduces the main characteristics of several typical permanent magnet motors and their main application occasions.
1. Rare earth permanent magnet generator Compared with traditional generators, permanent magnet synchronous generators do not require collector rings and brush devices, have a simple structure, and reduce the failure rate. The use of rare earth permanent magnets can also increase the air gap magnetic density, increase the motor speed to the optimal value, and improve the power-to-weight ratio. Almost all generators used in contemporary aviation and aerospace use rare earth permanent magnet generators. Permanent magnet generators are also used as auxiliary exciters for large steam turbine generators. In the 1980s, my country successfully developed the world's largest capacity 40 kVA~160 kVA rare earth permanent magnet auxiliary exciter, which was equipped with 200 MW~600 MW steam turbine generators and greatly improved the reliability of power station operation. At present, small generators driven by internal combustion engines for independent power sources, permanent magnet generators for vehicles, and small permanent magnet wind turbines directly driven by wind wheels are being gradually promoted.

  
2. High-efficiency permanent magnet synchronous motors Compared with induction motors, permanent magnet synchronous motors do not require reactive excitation current, can significantly improve the power factor (can reach 1, or even capacitive), reduce stator current and stator resistance losses, and have no rotor copper loss during stable operation, which can reduce the fan (small-capacity motors can even remove the fan) and the corresponding wind friction loss, and the efficiency can be increased by 2 to 8 percentage points compared with the same specification induction motors. At present, it is mainly used in oil fields, textile and chemical fiber industries, ceramic glass industries, and fans and water pumps with long annual operating time.
 
3. AC servo permanent magnet motors and brushless DC permanent magnet motors are now increasingly using variable frequency power supplies and AC motors to form AC speed control systems to replace DC motor speed control systems.
The permanent magnet synchronous motor powered by the inverter plus the rotor position closed-loop control system constitutes a self-synchronous permanent magnet motor, which has the excellent speed regulation performance of the electromagnetic DC motor and is brushless. It is mainly used in high control accuracy and high reliability occasions, such as aviation, aerospace, CNC machine tools, machining centers, robots, electric vehicles, computer peripherals, etc.
With the continuous improvement of people's living standards, the requirements for household appliances are getting higher and higher. For example, household air conditioners are not only large power consumption items, but also the main source of noise. Its development trend is to use permanent magnet brushless DC motors with stepless speed regulation. It can automatically adjust to the appropriate speed for long-term operation according to the changes in room temperature, reduce noise and vibration, make people feel more comfortable, and save 1/3 of electricity compared to air conditioners without speed regulation. Others such as refrigerators, washing machines, dust collectors, fans, etc. are also gradually switching to brushless DC motors.
4. Permanent magnet DC motor After using permanent magnet excitation, DC motor not only retains the good speed regulation characteristics and mechanical characteristics of electric excitation DC motor, but also has the characteristics of simple structure and process, small size, low copper consumption and high efficiency due to the elimination of excitation winding and excitation loss. Therefore, permanent magnet DC motors are widely used in household appliances, portable electronic devices, power tools and precision speed and position transmission systems that require good dynamic performance. At present, my country's automobile industry is developing rapidly. The automobile industry is the largest user of permanent magnet motors. Motors are key components of automobiles. In a super luxury car, there are more than 70 motors of various purposes, most of which are low-voltage permanent magnet DC micromotors. The starter motor for automobiles and motorcycles can reduce the mass of the starter motor by half by using neodymium iron boron permanent magnets and reduction planetary gears.



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