Composition and principle of pure electric vehicles

There is no big difference in structure between pure electric vehicles and traditional fuel vehicles. The body and chassis are the essential basic structural elements. In addition, the power supply system, electric drive system and auxiliary systems are the basic three unique to pure electric vehicles. Large structural elements. The composition of a typical pure electric vehicle is shown in Figure 1.

Composition and principle of pure electric vehicles
Figure 1 The structure diagram of a typical pure electric vehicle

The body shape of a pure electric vehicle is similar to that of a traditional fuel vehicle, but it is also quite different. Since the early pure electric car bodies were mainly improved from traditional cars, they inherited many styles of traditional fuel cars. In recent years, due to the continuous introduction of electric vehicle regulations and the continuous emergence of new usage requirements, pure electric vehicles have increasingly shown their own characteristics in the body shape, and have obvious regional characteristics. For example, Japan’s pure electric vehicle body design presents the characteristics of compactness, beautiful shape and liveliness, as shown in Figure 2(a). The United States still retains its traditional style full of power and sports in the shape of pure electric vehicles. Figure 2(b) shows the Tesla Roadster, the world’s first electric sports car produced by Tesla Motors. European electric cars. The styling is characterized by high-end luxury and fine detail, as shown in Figure 2(c) for the Peugeot pure electric sports car EX1.

Composition and principle of pure electric vehicles
Figure 2 Body shape of different pure electric vehicles

The chassis of a pure electric vehicle is basically the same as that of a traditional vehicle. The main differences are in three aspects: one is that its driving mode is different; the other is the braking energy recovery system is set in the braking system; the third is the power steering mechanism.
Pure electric vehicles use motors to replace traditional car engines, so the original location where the engine is installed can be used to assemble batteries and motors, so that the original driving methods of traditional cars can be used: In addition, the arrangement of batteries and motors on the chassis is more flexible , According to the design requirements, a variety of drive modes can be configured.
Pure electric vehicles cannot use the negative pressure generated by the vacuum of the intake manifold to brake like gasoline and diesel vehicles. Therefore, it is necessary to configure a special electric vacuum pump to generate negative pressure, or configure an electric hydraulic pump to generate oil pressure to provide brakes. Required braking force: In addition, the braking system of a pure electric vehicle needs to be equipped with a braking energy recovery device. When the vehicle is braking or decelerating, the motor/generator is converted into a generator to generate electricity and charge the battery.
The steering system of a pure electric vehicle generally uses an electric power steering system, which has a relatively high energy efficiency.

③Power supply system
The power supply system mainly includes power supply, energy management system and charging controller. Its function is to provide driving power to the motor, monitor power usage and control the charger to charge the battery.
Common power sources for pure electric vehicles include lead-acid batteries, nickel-cadmium batteries, nickel-hydrogen batteries, and lithium-ion batteries.
The energy management of pure electric vehicles and hybrid electric vehicles is different. Pure electric vehicles mainly refer to battery management systems. Its main function is to perform real-time monitoring, charging and discharging, inspections, temperature monitoring, etc. of battery cells and the entire group of electric vehicles.

④Electric drive system
The electric drive system mainly includes electronic controllers, power converters, motors, mechanical transmissions and wheels.
Its function is to efficiently convert the electric energy stored in the battery into the kinetic energy of the wheels, and can convert the kinetic energy of the wheels into electric energy to charge the battery when the car decelerates and brakes.
There are two main types of motors that are used in electric vehicles: DC motors and AC motors. When the drive system of an electric vehicle adopts a DC motor, although there are many unique features in the structure, such as no clutch, transmission, high starting acceleration traction, simple control system, etc., its overall power transmission system is low in efficiency. So it is gradually replaced by other drive types of motors. The AC motor drive system used in electric vehicles has outstanding advantages such as small size, low quality, high efficiency, wide speed range and basically maintenance-free, but its manufacturing cost is high. With the further development of power electronics technology, the cost will be reduced, and electric vehicles using this type of drive system will have strong vitality.
The performance of the electric vehicle control system directly affects the performance index of the vehicle. The control system controls the speed, acceleration and energy conversion of the car under various working conditions. It is similar to the accelerator pedal and transmission of a fuel car, including motor drivers, controllers and various sensors.
The controller is different for different motors. The DC/AC controller inverts the DC power of the battery into AC power and then drives the AC drive motor. The torque output by the motor drives the wheels through the transmission system to make the electric vehicle run.

⑤Auxiliary system
The auxiliary systems mainly include auxiliary power sources, air conditioners, power steering systems, navigation systems, wipers, radios, and lighting and defrosting devices. Except for the auxiliary power source, the auxiliary system differs according to different models. The auxiliary power source is mainly composed of auxiliary power supply and DCIDC power converter. Its function is to provide power to the power steering system, air conditioners and other auxiliary equipment.