The driving motors of new energy automobiles mainly include three types: permanent magnet synchronous motor, AC asynchronous motor and switch reluctance. Due to their different characteristics, they are used in different application occasions.
▌Rare earth permanent magnet synchronous motor:
According to the principle, PMSM has advantages of small volume, light weight, high power density, high reliability, high precision speed control, fast response. Due to the high power density of permanent magnet synchronous motor, its efficiency is up to 97%, so it can provide the biggest motivation and acceleration for vehicles. So it is basically used in new energy passenger vehicles with the highest requirement of energy volume ratio.
Its disadvantages are lower maximum power and higher cost. AC asynchronous motor is of low price, reliable operation; but its power density is lower, control is complex, speed range is narrow. Its price advantage makes it more widely used in new energy passenger cars.
▌Induction (asynchronous) motor:
It is able to withstand large working temperature changes. On the contrary, large temperature changes will damage the permanent magnet motor. The output torque of the induction motor can be adjusted in a wide range. No heat spreading mechanism is needed. It is of light weight, not more than 52kg. The speed range can reach 0-12000 RPM, so there is no need to install redundant transmission mechanism. Therefore, the vehicle body weight has great advantages in new energy vehicles.
The disadvantages are that rotor rotation speed is difficult to control, energy consumption is larger, power factor is lagged, structure is complex. The control system of induction (asynchronous) motor is complex, with higher manufacturing costs.
▌Switch reluctance motor:
It is of Low price, simple and reliable circuit, wide speed range; however, the vibration and noise are big, the control system is complex, and the pulse current to DC power supply is very large. It is used in large passenger vehicles, such as BYD electric cars.
Among them, Japanese and Korean vehicles mostly adopt permanent magnet motors, with relatively wider speed range and higher efficiency. However, they need to use the expensive permanent magnet materials Nd, Fe and B. European and American cars mostly use AC induction motors, mainly due to the shortage of rare earth resources and the consideration of reducing the motor cost. Its disadvantages are mainly the narrow speed range, low efficiency and the need for a governor with higher performance to match the performance.