Based on the characteristics of electric vehicles, there are higher requirements for the motor used. In order to improve the speed per hour, the motor should have higher instantaneous power and power density (w / kg); in order to increase the driving distance of one charge, the motor should have high efficiency; moreover, the electric vehicle is working at variable speed, so the motor should have high comprehensive efficiency of high and low speed; in addition, it has strong overload capacity, large starting torque and fast torque response. When starting and climbing, the speed of electric vehicle is low, but the required torque is large; when it runs normally, the torque required is small and the speed is very high. It has constant torque characteristic at low speed and constant power characteristic at high speed, and the operating speed range of motor should be wide. In addition, the motor should be solid, reliable, dustproof and waterproof, and the cost should not be too high.
At present, from the perspective of mature motor technology, switched reluctance motor seems to be more in line with the needs of electric vehicles in various technical characteristics, but it has not been popularized. Permanent magnet synchronous motor is widely used, such as Kia K5 hybrid, Roewe E50, Tengshi, BAIC eu260, etc. Tesla Model X and model s adopt asynchronous motor. In addition, if divided by current type, it can also be divided into DC motor and AC motor. Through the following table, we can first roughly understand the characteristics of four typical motors.
In the early development of electric vehicles, most electric vehicles use DC electric motor as driving motor. This kind of motor technology is relatively mature, with the characteristics of easy control mode and excellent speed regulation. It has been widely used in the field of adjustable speed motor. However, due to the complex mechanical structure of DC motor, its instantaneous overload capacity and the further improvement of motor speed are limited, and in the case of long-term operation, the mechanical structure of the motor will produce loss and increase the maintenance cost. In addition, when the motor is running, the sparks from the brush make the rotor heat up, which will cause high-frequency electromagnetic interference and affect other electrical performance of the vehicle. Due to the above shortcomings of DC motor, the current electric vehicle has basically eliminated DC motor.