In terms of technical indicators, domestic motors have the following differences compared with foreign motors:
1 peak speed
The peak speed is an important indicator for driving the motor, and it is also the most obvious indicator of the difference between the domestic drive motor and the foreign motor. The peak speed of most permanent magnet synchronous motors in China is below 10,000 rpm, while the foreign countries are basically above 10,000 rpm.
2 power density
Although the domestic motor can basically reach the international level in terms of power, there is a weight disadvantage under the same power condition, so the power density is far from the international level. At present, the power density of permanent magnet synchronous motors in China is mostly in the range of 1~2kw/kg, which is far from the target value of 3.5kw/kg in 2020.
3 efficiency
In terms of motor efficiency, the highest efficiency of domestic motors has reached 94% to 96%, reaching the level of Siemens, Remy and other companies. However, in terms of the area of high-efficiency area, there is still a certain gap in the proportion of the area where the system efficiency is greater than 80%. The area of high-efficiency area of electric motors in China is concentrated in 70% to 75%, while the foreign motors basically reach 80%.
4 cooling method
The cooling method of the motor has gradually evolved from natural cooling to water cooling. At present, domestic motor companies mainly use water cooling, and foreign advanced motor enterprises have developed oil-cooled motors. Some domestic motor companies have also developed oil-cooled motors, such as precision, to further improve the cooling efficiency of the motor.
Development bottleneck of permanent magnet synchronous motor
At present, the permanent electric synchronous motor is the main technical route for pure electric passenger cars, so how to further improve its performance has become a key issue in the industry. At present, permanent magnet synchronous motors face the following technical difficulties:
1 power density
There are two ways to increase the power, one is to increase the torque, and the other is to increase the speed. The main problem of the former is that the overload current is increased, resulting in high heat generation, which causes a large pressure on heat dissipation; the latter is a high-speed ferromagnetic loss, requiring high-performance low-saturation silicon steel sheets to increase the cost; or using a complicated rotor Structure, but affects power density.
2 materials
The permanent magnet material is also an important factor restricting the performance improvement of permanent magnet synchronous motor. The commonly used permanent magnet material NdFeB mainly has the disadvantages of poor temperature stability, irreversible loss and high temperature coefficient, and serious loss of magnetic properties at high temperature, thus affecting the motor. performance.
3 production process
The difficulty in the production process of permanent magnet synchronous motors is an important factor that restricts large-scale supporting passenger cars. Because of the lack of industrialization of permanent magnet synchronous motor manufacturers, domestic enterprises have high production non-performing rates and cannot meet the non-performing rate requirements of passenger car enterprises, especially with the expansion of the market size of pure electric passenger vehicles, 100,000-level The annual production poses a huge challenge for permanent magnet synchronous motors.
