Central issues:
Advantages of 42V automotive electrical system
Comparison of two schemes of automobile power supply system
Design of rare earth permanent magnet generator
solution:
Single car 42V single voltage solution
42V / 14V dual voltage solution
The voltage of the automobile power supply has been changed from 6V in the 1950s to 12V, which has a history of more than 50 years. Since 1990, automobile electricity consumption has increased by 5% to 8% every year. The development history and trend of its average electric load are shown in Figure 1. With the continuous advancement of automotive technology, more and more electrical and electronic systems will be applied to automobiles.
In the 1990s, automotive designers proposed the idea of ​​increasing the voltage of automobile power supply, which was quickly agreed by automobile researchers, automobile manufacturers, and component manufacturers, and related standards for 42V voltage of automobile power supply were formulated.
The transformation of the automotive power supply system from the existing 14V standard to the 42V standard has become an inevitable development trend, and will be rapidly developed in the next few years, resulting in a revolution in automotive electrical and electronic products. The implementation of the new automotive power supply system standard will have a huge impact on the traditional products of the automotive electronics industry. This is both a challenge and a rare opportunity for our country. We should actively participate in research and development in the process of automotive power supply reform and integrate with international automotive electrical and electronic products.
1 Advantages of 42V automotive electrical system
1.1 Safe and accessible voltage
According to the European safety law, the safe voltage of the human body is within 50V. Any system that exceeds 60V must have special insulation measures at the wires and connections, which will increase the weight and cost of the system. Therefore, the choice of 42V voltage is to meet the needs of electric energy, and like the traditional 12V system, even if it touches the electrode or the metal car body, it will not pose a threat to human safety.
The 42V voltage value is three times the output voltage of the current car generator 14V, and the 36V battery used in it is beneficial to use 3 traditional 12V lead-acid batteries for series modification.
1.2 Significantly reduce the cost of automotive wiring harness
Hyundai Motor has 2km of wires, more than 2,000 wire ends and more than 350 hubs. The 42V power system can greatly reduce the weight and cost of these harnesses. In theory, the same power is transmitted, the current of the 42V system is only one third of the 14V system, which reduces the current load of the motor and power components, and also reduces the transmission loss of the wires and power components to nearly nine One part, and can reduce the cross-sectional area of ​​the wire to reduce weight.
1.3 A large number of high-tech is widely used
With a 42V power system, many technologies that used to be impractical or impossible have become feasible. In the 42V electrical system, the wire control technology, ride comfort control device, electronically heated catalyst and solenoid valve system, active suspension and electric four-wheel auxiliary drive device can be used more effectively, providing more for the structural improvement of the vehicle Big possibility (Table 1).
Using the 42V power system, some long-running accessories of the engine such as power steering pumps, water pumps, cooling fans, air-conditioning compressors and air pumps are directly driven by the new power system, thereby reducing idling consumption and improving energy efficiency. For the electric brake system, which is directly driven by the power supply, the hydraulic or pneumatic system can be omitted, resulting in better driving comfort and better fuel economy.
1.4 Can greatly improve generator efficiency
The efficiency of silicon rectifier generators currently used in automobiles is below 60c / ~. The output current of the silicon rectifier generator is large, the current density of the armature winding reaches 10A / ram, and a lot of energy is consumed by the excitation winding, the armature winding and the rectifying element.
The 42V power system can provide a higher current output in the entire engine speed range, and the motor efficiency can reach more than 80%. Unitary door VDO products with a power of more than 8kw output 10 to 15kW, and the efficiency can reach 85%.
1.5 Conducive to the development of hybrid vehicles
After the 42V power supply is adopted, if the integrated power generation device (ISA) is activated, the following functions can be achieved:
â‘ When the car starts, the startup acceleration performance is enhanced, and the internal combustion engine is accelerated to exceed the idle speed in a short time (usually 0.1 to 0.2s), and then the internal combustion engine starts to ignite to achieve the engine without idle speed;
â‘¡ The car is in the parking state for a long time. If it encounters a red light, the control system will automatically cut off the fuel supply of the internal combustion engine, and the internal combustion engine stops running;
â‘¢ When the car is running normally, ISA is the working condition of the generator and charges the battery;
â‘£ When the car is accelerating or climbing, ISA works in the condition of electric motor to provide auxiliary propulsion power for the engine, so that the engine works in the high-efficiency area, which improves the efficiency and reduces the fuel consumption.
At present, the 42V electrical system structure has been recognized by the international automobile industry and has been adopted in some vehicles, such as Volvo ’s $ 80 and Ford ’s hybrid car Explorer.
2 Operating mode
In the new electrical system, there are two implementations: one is the 42V single-voltage solution for the entire vehicle; the other is the 42V / 14V dual-voltage solution.
2.1 Single voltage operation mode
The single voltage scheme of the 42V electrical system is shown in Figure 2. The single voltage of 42V will have a big impact on the current auto parts manufacturers, so it is difficult to promote.
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