Technical characteristics of high-voltage connectors for electric vehicles

Technical characteristics of high-voltage connectors for electric vehicles

In the three electrical systems of new energy vehicles, the high-voltage connection system plays a crucial role, just like the vascular system organically integrates various important organs of the human body. The battery is correct. The total negative circuit is similar to the human aorta and main vein, and each system circuit is similar to the human arteries, veins, and capillaries. To ensure the energy transmission of electric vehicles, the important guarantee for safe and reliable operation is to continuously transmit energy to various systems. Figure 6 shows the relationship between the high-voltage connection system and the three electrical systems.

2.1 Terminal Types

Currently, high-voltage connectors can be classified based on terminal type and structure.

1) Square terminal structure. Adopting stamping terminal technology, this type of terminal has low cost, high mold requirements, high mold cost investment, and is widely used for small current below 40A. TE terminals below 40A are very representative in the industry. There are some Japanese people American automotive companies use square terminal structures for high current connectors, such as Sumitomo, Yazaki, and other automotive companies such as Tesla. Toyota.

2) Circular terminal structure. Compared to stamped terminals, the cost of terminals is higher. However, due to the use of processing and production methods, there is no need or lower mold investment, resulting in less investment in the early stage of terminals. A more representative product, the TEHVA800 series, is a mainstream domestic product series.

2.1.2 Classification by structural type

According to the installation method, the connector structure can be divided into plugs and sockets. The plugs can be divided into linear plugs, 90 ° right angle plugs, sockets can be divided into flange sockets, 90 ° right angle sockets, linear sockets, etc.

2.2 High voltage interlocking

High Voltage Inter lock (HVIL), which uses low-voltage signals to manage high-voltage circuits, is a safe design method. In the design of high-voltage systems, in order to avoid power outage of high-voltage connectors during actual operation, high-voltage connectors should generally have the function of "high-voltage interlocking" caused by arcing caused by closure. The high-voltage connection system with high-voltage interlocking function should meet the following conditions when connecting and disconnecting: when connecting the high-voltage connection system, connect the power terminal first, and then connect the interlocking terminal; When disconnecting the high-voltage connection system, first disconnect the interlock terminal, and then disconnect the power terminal. High voltage interlocking is commonly used in high-voltage circuits, such as high-voltage connectors, MSDs, and other circuits in high-voltage distribution boxes.

Connectors with high-voltage interlocking can be disconnected through the logical sequence of high-voltage interlocking when energized. The disconnection time is related to the effective contact length difference between the high-voltage interlocking terminal and the power terminal, as well as the speed at which the disconnection occurs. Usually, the response time of the system to the interlocking terminal circuit is between 10 and 100ms. When the disconnection (unplugging) time of the connected system is less than the system response time, there is a safety risk of live plugging. Secondary unlocking is to solve the disconnection time problem. Usually, secondary unlocking can effectively control the disconnection time to over 1 second, ensuring safe operation.

2.3 Secondary unlocking

There are two ways to achieve secondary unlocking, one is through the sequence of operations, which is achieved through normal opposite or different directions. For example, the mainstream HVA800.HVC800 series high-voltage connector products in the market, when the connector is pulled out, the power wrench is exactly opposite or not in the same direction as the separation direction, increasing the response time when pulled out, and achieving secondary unlocking function. Another type is the mechanical secondary unlocking function. When unplugging the connector, only the position where the high-voltage interlock terminal is disconnected can be unplugged for the first time. In this state, the power terminals are still effectively in contact. At this point, due to the separation of the high-voltage interlocking terminal, the high-voltage circuit is disconnected, and then the power terminal is separated through a secondary operation to meet the functional requirements of two unlocks. Compared with sequential unlocking, mechanical secondary unlocking has higher safety, but its structure is relatively complex. Figure 9 shows the secondary unlocking process.

2.4 Locking structure

Connector Position Assurance (CPA) is a buckle structure used to increase the strength of the connector locking device. CPA can effectively protect the reliable connection of connector plugs and sockets, preventing safety accidents caused by accidents such as loosening or poor contact. CPA belongs to the auxiliary locking structure and meets the requirements of reliable locking by cooperating with the main locking structure. The working principle of CPA is that when the main locking structure is locked, CPA assists in locking, and the main locking structure is not susceptible to external environmental influences and looseness (except for main locking structure faults). When unlocking, it is necessary to unlock CPA to be able to unlock normally and meet the lock structure used under harsh conditions.

2.5 Terminal auxiliary structure

Terminal Position Assurance (TPA) (Figure 10) is a structure used for secondary protection and limiting of terminals, which prevents terminals from falling off under external tension and causing line interruption. It is used in harsh environments or high tension situations. This composition usually includes two types of retention structures, one is the retention structure of the terminal itself, and the other is due to the TPA retention structure.

2.6 Key parameter terminal crimping evaluation

Terminal crimping is a key process in the connector industry, and the evaluation of terminal crimping effect mainly consists of the following points.

1) Terminal tensile resistance. The evaluation of terminal crimping effect includes the minimum tensile strength of crimping between terminals and wires.

2) Terminal resistance. The evaluation of terminal crimping effect includes crimping resistance test evaluation.

3) Analysis of terminal crimping cross-section. Cut, polish, and cut the end face of the effective area of terminal crimping after crimping (select the densest compression area), and then conduct compression ratio testing with professional equipment. When magnified by about 5-10 times, there is no visible gap between the copper wires of the compressed cable, and the compression ratio should be controlled between 80% and 90%.

4) Terminal temperature rise. The temperature rise test generally requires a temperature rise of no more than 55K (different standards correspond to different requirements, and there are also 50K). The requirement of GB/T37133-2018 is 55K.

5) Definition of terminal voltage and high voltage width. For the definition of high voltage terminal and wide voltage terminal after the previous test was OK, and CPK control should be carried out during the process.

2.7. Comprehensive testing of high-voltage connectors requires comprehensive testing of product performance during offline production of high-voltage connectors and wiring harnesses. This comprehensive testing plays a very important role in checking product quality, generally including but not limited to the following testing items.

1) Voltage withstand test. Mainly targeting the risk of poor voltage resistance caused by changes in space or climbing distance during the assembly process of the product, or the risk of poor voltage resistance caused by wire harness crimping or other damage during the wire harness assembly process. Usually, this type of testing requires 100% testing.

2) Insulation testing. Mainly targeting the risk of poor insulation caused by changes in space or climbing distance during the assembly process of the product, or the risk of poor insulation caused by wire harness crimping or other damage during the wire harness assembly process.

3) The circuit is conducting. Mainly used for 2 or more sets of circuits, to detect whether each circuit corresponds one by one after connector assembly.

4) Air tightness test. Suitable for testing finished connectors or wire harness assemblies, applying 47.8kPa air pressure to detect the sealing of connectors, testing time, leakage value, and other parameters can be adjusted according to product characteristics.

5) Shielding circuit testing. Used to detect the resistance value in shielded circuits, the shielding resistance should generally be less than 10m Ω. The comprehensive simulation test bench (Figure 11) can achieve the main electrical performance testing (insulation), voltage resistance, conduction, etc. of connectors When the NG comprehensive testing platform program for air tightness testing is locked and accompanied by a flashing alarm light, a dedicated person needs to turn it on. OK unique barcode (2D code) labels can be automatically generated and printed to ensure that all offline products have been tested and traceable