Characteristics and applications of permanent magnet motors
Compared with traditional electric excitation motors, permanent magnet motors, especially rare-earth permanent magnet motors, have obvious advantages such as simple structure and reliable operation; small size and light weight; low loss and high efficiency; the shape and size of the motor can be flexible and diverse. . Therefore, the application range is extremely wide, covering almost all fields of aerospace, national defense, industrial and agricultural production and daily life. The main features of several typical permanent magnet motors and their main applications are described below.
 
1. Rare earth permanent magnet generator Compared with the traditional generator, the permanent magnet synchronous generator does not need the collector ring and the brush device, the structure is simple, and the failure rate is reduced. The use of rare earth permanent magnets can also increase the air gap magnetic density, increase the motor speed to an optimal value, and improve the power-to-mass ratio. Almost all generators used in contemporary aviation and aerospace use rare earth permanent magnet generators.
 
The permanent magnet generator is also used as the auxiliary exciter of the large-scale steam turbine generator. In the 1980s, my country successfully developed the 40 kVA~160 kVA rare earth permanent magnet auxiliary exciter with the largest capacity in the world at that time. Greatly improve the reliability of power station operation.
 
At present, Shanghai Power Transmission has learned that small generators driven by internal combustion engines for independent power sources, permanent magnet generators for vehicles, and small permanent magnet wind generators directly driven by wind turbines are gradually being promoted.
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2. Compared with induction motors, permanent magnet synchronous motors do not require reactive excitation current, which can significantly improve the power factor (up to 1, or even capacitive), reduce stator current and stator resistance losses, and There is no rotor copper loss during stable operation, which can reduce the fan (small-capacity motor 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 induction motor of the same specification. At present, it is mainly used in the fields of oil field, textile chemical fiber industry, ceramic glass industry and fans and pumps with long running time.
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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.
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The permanent magnet synchronous motor powered by the inverter and the closed-loop control system of the rotor position constitute a self-synchronizing permanent magnet motor, which not only has the excellent speed regulation performance of the electric excitation DC motor, but also realizes the brushless. It is mainly used for high control precision and high reliability. Sexual occasions, such as aviation, aerospace, CNC machine tools, machining centers, robots, electric vehicles, computer peripherals, etc.
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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, but also the main source of noise. The development trend is to use permanent magnet brushless DC motors with stepless speed regulation. According to the change of room temperature, it can automatically adjust to a suitable speed to run for a long time, reduce noise and vibration, make people feel more comfortable, and save 1/3 of electricity than air conditioners without speed regulation. Others such as refrigerators, washing machines, dust collectors, fans, etc. are also gradually switching to brushless DC motors.
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4. Permanent magnet DC motor After the DC motor adopts permanent magnet excitation, it not only retains the good speed regulation characteristics and mechanical characteristics of the electric excitation DC motor, but also has the advantages of simple structure and process, small size, and easy use due to the elimination of excitation winding and excitation loss. Low copper content and high efficiency. Therefore, permanent magnet DC motors are widely used in household appliances, portable electronic equipment, power tools, and precision speed and position drive systems that require good dynamic performance.