From large appliances like air conditioners, refrigerators, and washing machines to small items like fans, hair dryers, and shavers, electric motors are ubiquitous in our lives. Therefore, many people's understanding of electric motors is still limited to industrial motors used in household appliances. However, the automotive drive motors we're discussing today are quite different. In the era of traditional gasoline-powered vehicles, the engine was called the heart of the car because it was the core component for energy conversion. In the era of electric vehicles, the electric motor has become the new "power heart" of the vehicle. This "heart" faces special working environments such as limited installation space, harsh operating conditions, high vibration, high impact, and severe corrosion. Therefore, automotive drive motors need to have characteristics such as high density, small size, high power, high torque, reliability, durability, and low cost.
The "three major schools" dominate the drive motor
Having learned about the characteristics of drive motors, let's look at the current market situation. Currently, the drive motors for new energy vehicles can be mainly divided into three categories: switched reluctance motors, permanent magnet synchronous motors, and AC asynchronous motors. These three types of motors, according to their different structures and performance, are used in commercial vehicles and passenger vehicles respectively.
In the commercial vehicle sector, switched reluctance motors are commonly used. The name itself reveals two fundamental attributes of this type of drive motor: switching capability and reluctance. Switching capability means the motor must operate in a continuous switching mode, while reluctance refers to the variable reluctance magnetic circuit in the stator and rotor. Switched reluctance motors have significant advantages: simple structure, wide speed range, stable and reliable performance, and lower cost. However, they also have disadvantages such as large torque fluctuations, high noise, and system nonlinearity. These problems are unacceptable for passenger vehicles, hence their widespread adoption primarily in commercial vehicles.
A permanent magnet synchronous motor (PMSM) contains a rotor encased in permanent magnets. The stator generates torque to drive the rotor to rotate around its axis, and the magnetic fields of the stator and rotor are synchronized. Due to their high efficiency, high power density, and small size, these motors are mainly used in passenger vehicles and are highly sought after in the domestic market. However, their cost is high because permanent magnet materials are expensive. Major new energy vehicle manufacturers include BYD and Geely.
In order to generate induced current by cutting magnetic field lines, the rotor speed of an AC asynchronous motor is always slower than the speed of the rotating magnetic field of the stator, which is why it operates asynchronously. This type of motor has a relatively simpler structure and lower cost, but it has disadvantages such as larger size and heavier weight. It is used in both passenger cars and commercial vehicles, and representative automakers include Tesla and NIO.
"A Battle of Two Titans": The Love-Hate Relationship Between Passenger Vehicle Motors
After reading the above, we have a general understanding of the market distribution of these three types of motors. In the passenger vehicle sector, permanent magnet synchronous motors and AC asynchronous motors are mainly used. Since passenger vehicles are more closely related to our daily lives, it is necessary to discuss these two types of motors separately.
Those who follow new energy vehicles closely may be aware that most domestic OEMs prefer permanent magnet synchronous motors, while European and American manufacturers tend to use AC asynchronous motors. Domestic new energy vehicles such as the BYD Qin Pro EV500, the new generation Song EV500, Geely Emgrand EV, and Roewe ERX5 all use permanent magnet synchronous motors. Foreign OEMs, such as Tesla, use AC asynchronous motors in their Model S and Model X. However, there are exceptions; domestic manufacturers like NIO and Jiangling also use AC asynchronous motors. But apart from these well-known manufacturers, it's rare to see models using AC asynchronous motors.
Although permanent magnet synchronous motors currently have a larger market share, AC asynchronous motors were once widely used due to their strong overload capacity, good acceleration performance, and more stable structure. So why did permanent magnet synchronous motors buck this trend? The main reason is that AC asynchronous motors have high energy consumption, generate a lot of heat, are heavy, and require large cooling systems. These disadvantages directly forced companies like Tesla, specializing in AC asynchronous motors, to continuously increase vehicle size and energy density to maintain their range. It can be said that the disadvantages in energy consumption, weight, and size have firmly limited the development of AC asynchronous motors in the passenger vehicle sector.
Permanent magnet synchronous generators are taking the lead, and the initial signs of "unification" are emerging.
This "two-horse race" is quietly changing. Tesla, as a representative automaker of AC asynchronous motors, has switched to permanent magnet synchronous motors for its new Model 3. This motor change sends a key signal—permanent magnet synchronous motors are currently more suitable for passenger vehicles! What are the advantages of permanent magnet synchronous motors? Let's take BYD, a leading domestic OEM, as an example to find out.
As a veteran automaker that pioneered the new energy vehicle market, BYD has achieved considerable expertise in the field of permanent magnet synchronous motors. Its Dynasty series products feature drive motors that are lighter, smaller, and more efficient. By increasing the speed to 15,000 rpm, the motor achieves a 35% weight reduction while maintaining power output. For electric vehicles, weight reduction translates to less burden, and lighter weight translates to longer range. Furthermore, due to its inherent advantages, permanent magnet synchronous motors can be made smaller. BYD has integrated the drive motor, motor controller, and reducer into a single unit, reducing the powertrain size by 30% compared to separate systems. This saves more space for passengers, resulting in a more comfortable driving experience. In addition, compared to AC asynchronous motors, permanent magnet synchronous motors offer greater drive efficiency. For example, the new generation BYD Song EV500 features a permanent magnet synchronous motor with a maximum efficiency of 96%, ensuring efficient power output across most speed ranges. This is a crucial factor in the long range of pure electric vehicles.
Summarize
Currently, the three major motor types have each achieved success in different fields due to their respective characteristics. Switched reluctance motors have flourished in the commercial vehicle sector, while in the passenger vehicle sector, although permanent magnet synchronous motors and AC asynchronous motors each have their advantages, the permanent magnet synchronous motor camp has achieved better results in terms of market performance. For example, BYD, a long-established new energy vehicle company in China, has launched several blockbuster products this year, including the Yuan EV360, the new generation Song EV500, and the Qin Pro EV500, with sales repeatedly reaching new highs. All of these products are equipped with permanent magnet synchronous motors.
It is believed that with the development of the market, permanent magnet synchronous motors will continue to squeeze the market share of AC asynchronous motors in the pure electric passenger vehicle market in the next few years. If the existing technical problems cannot be solved in the future, the space for electric motors and more batteries will remain limited, and the survival space left for AC asynchronous motors in the market will become smaller and smaller.
