How to Choose the Right Motor for Your Electric Car?
According to the structure and working principle, there are three types of electric motor.
They are: direct-current motor, synchronous motor and asynchronous motor.
Direct-current motor motor is an early product. Direct-current motor needs routine maintenance (2-3 years) because there are carbon brushes inside, which will wear out during the rotation. What’s worse, spark will appear when changing direction. Thus, direct-current motor is not recommended for electric car.
Brushless direct-current motor (bldc motor for short) is developed on the basis of brushed direct-current motor. Permanent magnets are stuck on the rotor and demagnetization may occur. Furthermore, even with higher efficiency, it does not work on harsh environment. Usually, bldc motor is used in e-bicycle or scooter.
Synchronous motor mainly indicates permanent magnet synchronous motor (PMSM for short). Most PMSM motor is used as generator. Because the structure of PMSM is more complicated, thus, the cost is higher and there is also the possibility of magnetism-disappearing.
Asynchronous motor is alternating current motor (ac motor for short). Compare with bldc motor, the efficiency of ac motor is lower, but the torque is larger at the same power, which means ac motor has better climbing ability. Besides, after several years of development, the cost of ac motor is almost the same with bldc motor and it is free-maintenance.
It is better to use bldc motor if below 2kw, while 3-15kw ac motor, and if beyond 15kw, PMSM may be a suitable option.
Given that the climbing and overload ability, motor for electric car usually exceeds 3kw. Many clients asked if we have motor with bigger power such as 20kw or 30kw, but we do not suggest clients to use it. The reasons are as follows.
a. The price is much higher.
b. The bigger the power is, the more batteries are needed. At present, lithium battery is a little bit expensive while the volume of lead-acid batteries is large.
c. The maximum speed of 15kw ac motor can reach 120km/h.
To conclude, ac asynchronous motor is the best choice for electric car.