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The difference between new energy motors and industrial motors

Date:2022-05-26   Author:XINDA MOTOR

On the whole, electric vehicle motors and industrial motors are both types of motors, and the theories and methods of classification and control are the same. Unlike the industrial application of motors, motors used in electric vehicles usually require frequent starting and stopping, fast dynamic response, low-speed constant-torque operation, strong overload capability, wide speed variation range, and four-quadrant operation. While running the function, it should also meet the comfort of driving and the ability to adapt to the environment.

Compared with the drives of industrial motors, the drivers used in electric vehicle motors are quite different in size, working environment, reliability, power density, cooling method, etc. The basic requirements for electric vehicle motor drive technology are summarized as follows:

1. Strict volume requirements and weight requirements : Because it is a vehicle, the requirements in this respect are prominent. Ordinary industrial motors do not have such strict requirements on size and weight, and generally meet industrial goals as the first purpose. Different electric vehicles, size and weight determine the dynamic performance and driving experience of the vehicle, and directly affect the quality of the product. Therefore, the difficulty of electric vehicle motors is to improve the power weight density and power volume density. The smaller, lighter, and the more powerful the motor, the better. 

2. Unique torque characteristics : ultra-high torque is required at start-up or low speed, pumping the car speed to the desired speed in the fastest way. General industrial motors do not have such a high starting speed requirement. At the same time, enough power needs to be provided at high speed so that the car can cruise at high speed.

3. Wide speed regulation range : the maximum speed may be 4 times or even higher than the motor base speed. At present, the best solution for electric vehicles is to omit the multi-speed gearbox and use only fixed-speed gear sets. In this case, the wider the speed regulation range of the motor is required, the better. Taking Tesla's basic Model S as an example, the maximum RPM of the motor can reach 18,000 rpm, which is quite scary. This is a very big test for the power electronic governor. 

4. Full-range efficiency requirements : Unlike electric locomotives, which are powered by pantographs, electric vehicles are powered by batteries, and the cruising range depends entirely on motor efficiency. For every 1% increase in motor efficiency, the cruising range can be correspondingly increased by 1%. Therefore, the requirements for the efficiency of the motor are very high. A little higher is victory, and every bit of energy must be optimized.

5. High reliability and stability in the vehicle operating environment: A high degree of safety should be ensured under any circumstances, especially controllable in failure mode.

6. Low noise : including electromagnetic noise and audio noise, to meet the needs of vehicle electromagnetic compatibility and driving comfort.

7. Reasonable cost : Cost has always been a big obstacle to the adoption of electric vehicles.

The indicators for evaluating a motor drive system mainly include external characteristics (the relationship between maximum output torque and speed), constant power speed regulation range, and drive system efficiency distribution map (not a certain point of efficiency, nor the efficiency of a separate motor body or controller) , drive system power density and torque density.

▼  The following pictures clearly point out the relevant differences between automotive motors and industrial motors:


Comparison of advantages and disadvantages of various new energy motors

The drive motor is one of the three main parts of new energy vehicles. If the battery system is the blood of the electric vehicle and the electronic control system is the brain of the electric vehicle, then the motor system is the heart of the electric vehicle . In the new energy vehicle, the electric motor is used to replace the engine, and under the control of the motor controller, the electric energy is converted into mechanical energy to drive the vehicle, which is the only driving device of the pure electric vehicle.


Survival of the fittest

At present, the classification of motors mainly includes DC, AC induction, permanent magnet synchronous and switched reluctance. At present, permanent magnet synchronous is the mainstream motor type due to its better performance. The price of AC asynchronous motors is moderate, but the performance is slightly worse, and some manufacturers use them in the United States and China. The main advantage of the switched reluctance motor is its lower price, but there are also technical problems of noise and vibration. If these problems can be solved, the switched reluctance motor will have a large market. At this stage, the drive motors suitable for new energy vehicles mainly include permanent magnet synchronous, AC asynchronous and switched reluctance . Because of their different characteristics, each has its application.

The permanent magnet synchronous motor is small in size, light in weight, high in power density, high in reliability, high in speed regulation accuracy and fast in response speed; however, the maximum power is low and the cost is high. Because the permanent magnet synchronous motor has the highest power density, its working efficiency can reach up to 97%, and it can output the maximum power and acceleration for the vehicle. Therefore, it is mainly used in new energy passenger vehicles that require the highest energy-to-volume ratio. The AC asynchronous motor is low in price and reliable in operation; however, its low power density, complex control, and small speed regulation range are inherent limitations. The price advantage makes it widely used in new energy buses. Switched reluctance motor has low price, simple and reliable circuit, and wide speed regulation range; however, it has large vibration and noise, complex control system, and generates large pulse current to DC power supply, so it is used in large passenger cars.


The new energy vehicle drive motor is developing towards: small and lightweight; high efficiency; better torque characteristics; long service life, high reliability; low noise; low price. 

Permanent magnet synchronous motor has become the mainstream trend

At present, the use of permanent magnet synchronous motors in China's new energy vehicles accounts for more than 90% , and AC asynchronous motors are mainly used by American car companies led by Tesla and some European companies. On the one hand, this is related to Tesla's initial technical path choice. The AC induction motor is cheap, and its large size does not hinder American cars. Excellent. Permanent magnet synchronous motors are still the most widely used motors for new energy vehicles in other countries, including China and Japan. The main factor is that it is suitable for the national road conditions. The permanent magnet synchronous motor can still maintain high efficiency during repeated start and stop, acceleration and deceleration, and is the best choice for the limited working conditions of the expressway network. In addition, my country is rich in rare earth reserves, and Japan's rare earth permanent magnet industry has a supporting foundation is also an important factor. Japan's Toyota, Honda, Nissan and other car companies basically use permanent magnet synchronous motor drive systems, such as Toyota's Prius, Honda's CIVIC. Because in Japan, there are many companies supplying rare earth magnets for permanent magnet motors, and most cars drive at medium and low speeds, so it is more appropriate to use permanent magnet synchronous motors with higher efficiency during acceleration and deceleration. Japan is a world leader in the development of hybrid vehicles, most notably the Toyota Prius. On the whole, new energy vehicle motors have higher technical requirements, and permanent magnet synchronous motors have the most advantages. The drive motor is one of the three core components of new energy vehicles. Compared with traditional industrial motors, new energy vehicle drive motors have higher technical requirements. From the perspective of comprehensive performance, permanent magnet synchronous motor has the most advantages and can better represent the development direction of new energy vehicle drive motors. Since China is extremely rich in rare earth reserves and the motor technology is close to the world's advanced level, it is expected that permanent magnet motors will occupy the motor market of China's new energy vehicles for a long time. 

Motor development technology trends

In general, permanent magnet synchronous motors have obvious advantages over induction motors. However, the current cruising range of pure electric vehicles is bound to be an extremely important indicator, and the high efficiency of the permanent magnet synchronous motor can better improve the cruising range. Moreover, the successful development of NdFeB permanent magnets with high heat resistance and high magnetic properties and the further development and improvement of power electronic components have further improved the development of rare earth permanent magnet synchronous motors. But as far as the current development trend is concerned, the permanent magnet synchronous motor seems to have a better prospect. 

With the rapid development of new energy vehicle drive technology, many new structures or new concept motors have been put into research. Among them, the new permanent magnet brushless motor is one of the most promising motors, including hybrid excitation type, hub type, double stator type, memory type and magnetic gear compound type . In addition, amorphous motors have also begun to enter the field of new energy vehicles. As a new generation of high-performance motors, their own advantages will certainly play a huge role in promoting the development of the new energy vehicle industry.