First, high voltage, high current
1. The electric vehicle refers to a fully powered by a battery wheel drive electric vehicles, operating voltage up to several hundred volts, for example: BYD e5 battery voltage 633.6V. .
2 hybrid vehicle battery, although not the only source of driving force, but the assembled battery voltage Is also high, for example: Corolla hybrid battery voltage Is 201.6V, the boosted voltage Is as high as 650V. They are much higher than human safety voltage of 36V.
3. The U.S. Automotive high-voltage dIscharge current system works and sometimes up to hundreds of security, but human safety Is the current 50mA.
Second, high pressure safety hazards
when the high voltage circuit failure, may directly endanger the lives of occupants and property. For example: high voltage insulation breakage, short circuit and the drain when a high voltage cable and the like occur.
Well, some people Will ask, since the high-voltage so dangerous, Why manufacturers should continue to boost the voltage of new energy vehicles it? In addition to increased by raIsing power voltage, the external torque Is increased, our analysIs to other reasons:
Third, a certain power, increasing the voltage, the wire harness Is reduced cross-sectional area
1. according to the formula P = UI, when the power Is constant, the voltage and current inverse relationship. For example: 120KW power such as 12V power, current 10000A; such as 600V supply, current 200A.
2. According to GB / T4706.1-2005 national standards, harnesses thickness (i.e. a copper wire cross-sectional area) versus load current, we can calculate the load current Is 200A, the wire You should be more duffel?
1 mm2 copper wire allows the long-term load current 8A-12A 1.5 mm squared Copper long lines allow the load current 12A-15A 16 mm 2 or smaller, per square. 6A copper, aluminum per square 4A 16-70 mm, copper per square. 5A, aluminum per square 3.5A S = cross-sectional area of copper 200A / 5A = 40 square millimeters. Do you dare to imagine, 10000A load current corresponding harness the cross-sectional area in the end how much?
Source: Ogilvy grid
At the same time, the cross-sectional area of the wire harness can also lead to an increase in Automotive wiring harness heavy, hard core cooling, space the arrangement Is difficult, the cost increase and the like. Therefore, an appropriate increase in voltage, choose a reasonable cross-sectional area of the wire harness obvious.
Fourth, the less energy loss
power loss mainly loss harness resIstance heating caused by the harness resIstance heating most the main thing Is current and relevant. P = UI power Is proportional to voltage and current, then the higher the voltage the same current power delivery smaller, resulting in less current harness smaller heat resIstance, so the smaller power loss.
Conclusion: increase the current Will make the harness thicker, increase power loss, improve voltage and high-voltage safety aspects and parts challenges, I believe the U.S. Automotive design masters Will make more informed decIsions.