When the high-voltage system is working, the current is as high as tens of amps, or even hundreds of amps. Compared with traditional low-voltage connectors, high-voltage connectors need to withstand higher voltage and current. Facing harsh environments such as car vibration, bumps, rain, snow, and sand, The probability of failure of the high-voltage connection system is also greatly increased, and once a problem occurs, overheating will affect the function of the vehicle, or it will cause a combustion accident and threaten the safety of users. Therefore, new energy vehicles put forward higher requirements for the safety and reliability of high-voltage connectors.
In order to ensure the quality of high-voltage connectors, manufacturers will conduct comprehensive tests on electrical performance, mechanical performance, air tightness, and environmental adaptability when they are off-line, but this does not guarantee that high-voltage connectors are safe and reliable in the later use process . Field use and experimental data show that among the various failure modes of automotive high-voltage connectors, electrical contact failure accounts for the largest proportion, about 45%. The various failure modes and their proportions are shown in the figure below. Major manufacturers have done a lot of work in preventing high-voltage connector failure design, such as the common high-voltage interlock function, but in the terminal market, there are still many high-voltage connector failure problems.
01 Electrical contact failure
The reasons for electrical contact failure generally include insufficient electrical contact pressure, contact wear, etc. The structure of the high-voltage connector for new energy vehicles is shown in the figure below, which is mainly composed of contacts, shielding layers, housings and accessories. Among them, the contact piece is responsible for transmitting electric energy, which is the main weak link causing electrical contact failure. Due to vehicle vibration, eccentric insertion, metal deformation, foreign object interference, etc., the contact piece of the high-voltage connector is in poor contact and the contact resistance increases. When a large current passes through, the heat is serious.
02 Insulation failure
There may be moisture and corrosive substances on the surface of high-voltage connectors that fuse with the surface water film to form ionic conductive channels. The reason for this result is that part of the insulating surface is difficult to clean, so it must be strictly screened during the quality inspection process. It should be noted that the voltage for testing insulation resistance is DC, while the test for dielectric strength is AC. The power for testing insulation resistance is much lower than the power for testing dielectric strength.
03Mechanical connection failure
The mechanical connection failure of electrical connectors manifests as a variety of failure modes, which are inseparable from the process and use process. Welding, crimping, installation and stress state are the weak links of mechanical connection. The failure of mechanical connection usually exposes problems during use. For products with relatively high requirements, early screening and evaluation tests can be carried out to improve the reliability of use.
In fact, with the development of science and technology, people need to solve more and more failure problems of high-voltage connectors, and the failure modes of high-voltage connectors are far more than these. and many more. Early screening and evaluation tests can be carried out in actual production operations. High-voltage connectors are the link between high-voltage components of new energy vehicles, and their reliability directly affects the function and safety of vehicles.
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