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A permanent magnet motor is a type of synchronous motor whose rotor uses permanent magnets. The stator generates an electromagnetic torque to push the rotor's magnetic field around the axis line. The stator and rotor's magnetic field are synchronized. Permanent magnet synchronous motor is widely used in domestic electric vehicles.
Permanent magnet synchronous motor, because compared with ac asynchronous motor, it has the following advantages:
High efficiency, more electricity saving
Compared with three-phase asynchronous motors, permanent magnet synchronous motors not only have higher efficiency at rated power points, but also have higher average efficiency over the entire speed range. The excitation field of permanent magnet synchronous motor is provided by permanent magnet, and the rotor does not need excitation current, and the motor efficiency is improved. Compared with asynchronous motor, the power is saved at any speed point, especially when the speed is low. Simply put, permanent magnet synchronous motors save more power and help improve the driving range of electric vehicles.
Greater starting torque, less noise, lower temperature rise
Permanent magnet synchronous motor generally adopts asynchronous starting mode, because the rotor windings do not work when the permanent magnet synchronous motor works normally, in the design of permanent magnet motor, the rotor windings can fully meet the requirements of high starting torque, such as making the starting times 1.8 times to 2.5 times, or even larger.
Small size, light weight, is conducive to the vehicle lightweight, reduce energy consumption of electric vehicles
Due to the use of high-performance permanent magnet materials to provide magnetic field, the air gap magnetic field of the permanent magnet motor is larger than that of the induction motor, and the volume and weight of the permanent magnet motor can be greatly reduced compared with the induction motor. For example, the weight of the 11kW asynchronous motor is 220kg, while the permanent magnet motor is only 92kg, equivalent to 45.8% of the weight of the asynchronous motor.
Simple and flexible motor structure, strong reliability
The nd-fe-b permanent magnet material needed to manufacture permanent magnet synchronous motor is rare earth resource. For countries lacking rare earth resources or underdeveloped rare earth industry, there is no way to start. China has 70% of the world's rare earth resources, the total production of Ndfeb magnetic material reaches 80% of the world, European and American car companies if they want to use permanent magnet synchronous motor electric vehicles need to consider the import of rare earth. Therefore, Tesla and other foreign brands have to use more backward AC asynchronous motor, because they do not have the ability to produce permanent magnet synchronous motor, which can also reflect that China's electric vehicle technology has been in the forefront of the world in some fields, the realization of "curve overtaking" is not impossible.