High voltage interlock connector

the concept of high-voltage interlock is introduced in the connection design

1.2.2High voltage interlock (HVIL)

In terms of the entire high-voltage interconnection system, in order to ensure the safety of the high-voltage system when it is powered on and off, the concept of high-voltage interlock is introduced in the connection design. The simple description is that when the connector is plugged and turned on, the high-voltage circuit is first contacted and turned on, and then the high-voltage interlock signal circuit is turned on; when disconnected, the high-voltage interlock signal is disconnected first, and then the high-voltage circuit is disconnected. Most connector manufacturers put the high-voltage interlock design inside the connector, and some manufacturers put the high-voltage interlock outside the mating cavity through the auxiliary structure design. It is very important to ensure the stability of the high-voltage interlock circuit. If the high-voltage interlock is not continuous, the possible impact will be very bad. For example, when the car is driving, the signal of the high-voltage interlock circuit is abnormal, causing the whole car to suddenly lose power and fail to operate normally, which may cause a traffic accident.

1.2.3  High-voltage interlocking locking structure

Understand that the real secondary lock does not have a secondary protection function, but more effectively protects it. The real meaning is that after the primary lock, if the primary lock fails or no operation is verified in place, the secondary lock is It is a very important function to ensure that the first lock is protected after the first lock is locked. The most commonly used mechanism in the secondary locking structure combined with the primary lock is the moment arm mechanism. Because the primary locking is related to the insertion and extraction force, a form similar to the moment arm mechanism is required according to the mechanical design concept, so as to achieve both labor saving and The connector can be easily inserted in place.

For the requirements of the force arm, USCAR talks about a lot of ergonomic operability of the force arm. The USCAR also stipulates the force requirements of the related primary and secondary locks in the case of mating and mismatching. In fact, most of us would think that USCAR is the standard for connectors, but I think that the USCAR standard is not only a technical standard, but also guides designers to make the structure reliable in the design process, and how to make the structure and performance reliable under the premise of reliable structure and performance. , Can also provide customers with a better product experience. The picture below is a picture of a more common locking structure product.


1.2.4 High-voltage connector protection level

The protection of the connector is mainly divided into three arrangements:

The first is the board end seal: the board end is the connector socket end using four screws to install mechanically. This is a more commonly used structure, but there are also some special structures

high-voltage cable、high-voltage connectors、HVIL

high-voltage cable、high-voltage connectors、HVIL

The second is the plug-to-head seal: the plug-to-head plug means that the male end contains the female end or the female end contains the male end with rubber parts for protection between the radial and axial directions

high-voltage cable、high-voltage connectors、HVIL

high-voltage cable、high-voltage connectors、HVIL


The third is the wire end seal, the protective seal between the wire end connector and the cable

With the development of the market for high-voltage connectors for electric vehicles, the performance requirements of OEMs for product protection are also constantly improving. In the early stage of industry development, the protection requirements of IPI67 can already satisfy most customers. However, in the later period, as the protection failure of connector products appeared on the market, there were more and more cases of product leakage, insulation failure, and even ablation.

he gradual improvement of protection requirements has become the development trend of electric vehicles. The current IP67 requirements cannot meet the normal use requirements. Of course, this is not absolute, and it depends on the location of the connector on the vehicle. According to the layout of the high-voltage circuit in the whole vehicle, it will be suspended under the chassis of the car. It is a principle that high-voltage must not enter the cabin. Therefore, most high-voltage connectors are located on the chassis close to the ground or close to the wheel hub. When the weather is bad, such as severe weather, heavy rain, or some severe cold weather, the water carried by your tires will actually impact these connectors. If you are familiar with the test, the domestic standard does not have IP6K9K. It is found that if IP67 is used, the impact pressure of the high-pressure water gun is actually not as great as 6k9k. When the car is running at high speed and suddenly wading into the water, the instantaneous water pressure rushing to the connector will be very large, so sometimes it is difficult to meet the actual use requirements of IP67. In response to this, the current domestic standard QC/T1067 and the foreign standard USCAR divide the connector seal into two levels S1 and S2. For the S2 level, it is clearly stipulated that the applicable occasion is the lower position of the chassis, and 6K and 9K are recommended, so if the protection is connected in the future, it must be 6K and 9K. If the connector is not arranged in the above position, the IP67 design can actually meet the requirements of the entire vehicle.


1.2.5 Electromagnetic shielding

Electric vehicles have many electronic devices, and electric current will generate magnetic fields, and the whole vehicle parts must have the ability to resist interference. Especially as electric vehicles are now a carrier, unmanned driving will be developed more on this basis, so this technical issue is very important. For high-voltage systems, shielded connectors and cables are very important, but we have to give priority to system-level layout. This is a prerequisite. If your OBC, the location of your layout, including the system DCDC itself may have some congenital problems, no matter how good the connector is, there will be various signal interference problems, so we must first consider the system type, and then consider the component level. Regarding the shielding effectiveness of the connector, two methods are generally adopted.

In the first way, we have a metal shield on some plastic connectors, and the cable shield will be connected to the shield of the metal shell to form an effective 360° shield. In the second way, most high-voltage and low-current connections will not have a secondary connection, and will be connected to the shielding layer of the cable. This method is also commonly used by existing manufacturers, including some of the more well-known domestic ones. OEMs are also considering this approach. We call it spring contact (English), which is actually a spring connection. The benefits of this structure are also many, because the size and space will be smaller, and its contact points will be more; there are many manufacturers of this structure, mainly represented by companies such as BMW Spring in Switzerland and Basel in the United States. They There are many practical and mature application cases in this area.

In most cases, the connection between the wire and the shielding layer will be crimped in the form of metal inner and outer rings. The shielding layer is placed between the two metal rings, and the shielding layer and the metal ring are deformed by cold pressing. Tightly fix. In addition, we also have a shielding method, which uses a structure similar to a watchband spring to replace the spring connection. This structure is often used in Harsh Environment products and has mature technology; we have done relevant tests and can meet the design requirements . The structure is applied to the shielding of new energy electric vehicles, which can not only meet the performance requirements, but also is a punched part, suitable for mass production and high cost performance.

1.2.6Connector material

The material of the connector insulation is generally PA66, PBT, ABS, PC, etc. The contact material is generally made of brass, phosphor bronze, beryllium copper, etc., but the most commonly used materials abroad are copper-nickel-silicon materials. The connector shell material is generally divided into two kinds of materials: plastic and metal.

1. Lightweight

Due to the demand for lightweight vehicles, especially passenger car manufacturers, under the premise of meeting product performance, they will try their best to choose plastic connectors to control the weight of the vehicle.

2.Product use environment

Because the mechanical strength of metal materials is better than plastic. Therefore, in some harsh environments, metal connectors are more suitable. For example, special vehicles, muck trucks, and electrical connection parts that are not protected during the layout of the entire vehicle. At this time, metal connectors are slightly better than plastic connectors in terms of environmental impact and mechanical strength.

3.Shielding implementation

Regarding the shielded connector, since the shell of the metal connector itself is used for conducting the shielding, it forms a carrier for shielding protection. Under normal circumstances, metal connectors are easier to achieve better shielding effectiveness than plastic connectors, and the appearance structure is more compact.



The development trend of high-voltage connectors

The development trend of high-voltage connectors

1  Policy-oriented role

The formulation of the country’s new energy electric vehicle industry policy should be determined in accordance with China’s national conditions. Regarding the development of a green transportation system, the national plan proposes to accelerate the upgrading of vehicle and ship structure and promote the use of new energy vehicles. By 2020, the production and sales of new energy vehicles will reach about 2 million. Accelerate the use of new energy or clean energy vehicles in new and updated public transportation, sanitation, postal, rental, commuting, and light material distribution vehicles in urban built-up areas, and the use of key areas will reach 80%; key areas of ports, airports, railway freight yards, etc. The addition or replacement of work vehicles mainly uses new energy or clean energy vehicles.

Before the end of 2020, all buses in logistics parks, industrial parks, industrial parks, and large-scale separate cities will be replaced with new energy vehicles. Build centralized charging piles and fast charging piles in logistics distribution centers such as logistics parks, industrial parks, industrial parks, large commercial shopping centers, and agricultural wholesale markets. According to the country’s policy orientation, automakers also adjust their internal models in accordance with relevant policies, which determines the development direction of the connector.


2 Platformization and customization

There are also many types of electric vehicles, such as passenger cars, logistics vehicles, including custom connectors. The requirements will be different, or some special requirements will be put forward, so they include unmanned driving, Internet of Things vehicles, New energy, etc., our connector manufacturers should consider, this kind of customization of electric vehicle industry needs (vehicle end and battery end), I think it may be a good choice, we are now moving towards first step. Because in general, these types of cars will be used in different occasions. In fact, they are all subdivisions. Although the volume is not that large, the market belongs to us. We are top-notch in this market. This is also a Good choice.

The second is platformization. In the future, batteries and vehicles will become platform-based. How to maintain in-depth technical communication with customers and form a platform-based product for both parties is very important. There are more domestic OEMs, and everyone’s platforms are different now, such as batteries. There are a lot of whole package factories, and each has its own module solution and battery box group solution. As a connector manufacturer, you need to think about how to make platform-oriented applications.


3 Miniaturization and lightweight

Under the background of the auto industry’s increasing pursuit of energy saving and environmental protection, the lightweight and miniaturization of automobiles has become a technological trend, and it is also the focus of auto manufacturers’ technical competition. By controlling the weight of the entire vehicle, it can effectively reduce fuel consumption, reduce exhaust emissions, and increase fuel consumption. efficiency. In a big environment like the automobile industry, the new energy connector must also be miniaturized and lightweight.

A series of important solutions for the miniaturization and lightweight of automobiles, including the introduction of smaller-sized high-performance copper alloy wires as signal transmission lines, and the introduction of terminals and contact systems that are developing towards miniaturization, as well as the crimping produced by this miniaturization Unstable optimization and reliable verification methods; the principle of using high-performance terminals to reduce the size of low-power transmission wires, and the use of aluminum wires instead of large-diameter copper wires that transmit higher power.

Application parameters of high-voltage connectors in automobiles

Application parameters of high-voltage connectors in automobiles

(1) Use position: As the name suggests, it is the application position of the connector on different high-voltage electrical appliances in the vehicle. Choose the connector.

(2) Rated voltage: the maximum voltage at which electrical equipment (including electricity and power supply equipment) can work stably for a long time.

The rated voltage is proportional to the creepage distance & electric clearance. In other words, the higher the rated voltage requirement, the larger or longer the connector. The design standard of creepage distance & electric clearance is in accordance with GBT 16935.1 (IEC 60664-1)

(3) Rated current: The rated current of electrical equipment refers to the maximum current that is allowed to pass for a long time when the heat does not exceed the long-term allowable temperature of heat under the rated voltage working condition under the reference ambient temperature.

For electric vehicles, P=UI, and the rated current is determined by the power P of the electrical equipment and the output voltage U.

Peak current: The maximum current value generated by an electric vehicle at the moment of rapid acceleration, climbing, or overload.

The current-carrying cross-sectional area is proportional to the rated current of the connector. In other words, the larger the pin/hole/wire cross-section, the larger the current it can pass, and the larger the connector.

(4.1)Design HVIL function purpose

Confirm the integrity of the entire high-voltage system. When the circuit of the high-voltage system is disconnected or the integrity is damaged, the safety measures of the whole vehicle will be activated.

(4.2)Realization of HVIL function

a. The entire system needs to be structured, which must be designed during system development;

b. Mainly through the connector to complete;

c. The HVIL circuit is a low-voltage circuit, which is independent of the power circuit.

(4.3)The realization principle of connector HVIL function

The power and signal terminals should meet:

——When connecting, the power terminal is connected first, and the signal terminal is connected later.

——When disconnected, the signal terminal is disconnected first, and the power terminal is disconnected later.

Special note: the connection of the power terminal indicates a good contact, and a virtual contact is unacceptable

(5) shield

Alternating electric field shielding: In order to reduce the coupling interference voltage of the alternating electric field to the sensitive circuit, a metal shield with good conductivity can be set between the interference source and the sensitive circuit, and the metal shield can be grounded. The main difference between shielded and unshielded connectors is whether a metal shield with good conductivity is provided.

(6) Protection level

The IP protection level is composed of two numbers. The first marked number indicates the level of protection against dust and foreign objects. The second marked number indicates the degree of airtightness of the appliance against moisture and water intrusion. The larger the number, the protection. The higher the level.

(7)Way out

Mainly refers to the angle between the outlet angle of the cable at the end of the electrical connector plug and the normal direction of the socket installation surface. According to this division, there are common 90° (curved) and 180° (straight) outlet electrical connectors.

(8) Socket installation method

In order to meet the needs of OEM designers for different arrangements of connectors


Precautions for the installation of high-voltage connector sockets

Precautions for the installation of high-voltage connector sockets

(1)The voltage selection needs to be matched: the rated voltage of the whole vehicle after load calculation should be less than or equal to the rated voltage of the connector. If the working voltage of the whole vehicle exceeds the rated voltage of the connector for a long time, the electrical connector has the risk of creeping and ablation.

(2)Current selection needs to be matched: the rated current of the whole vehicle after load calculation should be less than or equal to the rated current of the connector. If the working current of the whole vehicle exceeds the rated current of the connector for a long time, the electrical connector may be overloaded and ablated.

(3) Cable selection needs to be matched: the vehicle cable selection and matching are divided into cable current-carrying matching and cable and connector sealing matching. Regarding cable current-carrying, each main engine factory has specialized electrical engineers to carry out matching design, which will not be explained here. .

Seal matching: The connector and cable seal rely on the elastic compression of the rubber seal to provide the contact pressure between the two, thereby achieving reliable protection performance, such as IP67; according to calculations, the realization of a specific contact pressure depends on the specific compression of the seal, and accordingly Introduced, if reliable protection is required, the sealing protection of the connector has specific size requirements for the cable at the beginning of the design;

The current-carrying section of the same specification, the cable can have different outer diameters, such as shielded cable and unshielded cable, national standard cable and LV216 standard cable, which cable is specifically matched, the connector selection specification has a clear statement, so connect Particular attention should be paid to the specification requirements of the adapter cable when selecting the type of the connector to prevent failure of the connector seal.

(4) The whole vehicle needs flexible wiring: For the wiring of the whole vehicle, each OEM has requirements for bending radius and slack; according to the use case of the connector in the whole vehicle, it is recommended that the connector terminal itself is not stressed after the wiring harness is assembled. Only when the wiring harness as a whole is subjected to vibration or impact due to the vehicle’s operation, the strain relief is achieved through the flexibility of the wiring harness. Even if a little strain is transmitted to the connector terminals, the stress generated does not exceed the design holding force of the terminal in the connector.

 Analysis of key items in the design of high-voltage connectors

Temperature rise is one of the most important design key items in connector design. Abnormal temperature rise will cause ablation of the connector due to excessive temperature rise.

The temperature rise of the connector is affected by the following factors:

1. Contact resistance: used for conductive connection, the resistance between two contact carriers, such as pinhole-to-plug contact resistance, pinhole tail and wire crimp resistance, threaded connection copper plate and copper plate contact resistance

2. Material environment heating: When the connector is in a high temperature environment for a long time, because the materials used in the connector are engineering plastics, metal, rubber, etc., especially engineering plastics require a maximum operating temperature of 140 ℃, but when the product is used in an environment that is too high , When the connector heats up due to its own contact with internal resistance when it reaches thermal equilibrium, plus the ambient temperature is higher than the maximum working temperature allowed by the material. At this time, if the connector is in this environment for a long time and the internal temperature cannot be discharged due to the heating of the internal pinholes of the connector, the internal temperature will continue to rise, and the connector will generate a lot of heat, causing the connector to ablate It causes the vehicle to burn, which is a very serious problem. Both rubber materials and metal materials have maximum operating temperature limits, and both need to be considered during design.

3. The connection of the plate end: when bolts are used in the design, or preventive measures should be taken to prevent loosening during the supply; at the same time, when the bolt is connected, the torsion test must be carried out according to the operating specifications. In the case of screw connection of conductive parts, one of the main failure modes is that the tightening torque is not controlled in accordance with the torque requirements, resulting in abnormal temperature rise and ablation of the connection part.

4. Derating curve: Now let’s discuss the derating curve. In my understanding, the derating curve is like choosing a product. This product should be used in a specific environment. At this time, when choosing a product, According to an attribute value of this product, determine which range of products you choose. The derating curve diagram of the high-voltage connector is to provide customers with a menu, and customers choose their own suitable dishes according to their tastes according to this menu.

The derating curve is the different values corresponding to different currents under different working environment temperatures. These values are a graph obtained by the dot method. With this derating curve graph, the use conditions of the connector can be seen more intuitively.


The figure below is an illustration of the temperature rise and derating curv

Temperature rise and derating curve value


Temperature rise graph


Derating curve



Application of high voltage connector in vehicle system

Connectors for new energy vehicles are one of the major categories of connectors. In recent years, with the development of new energy vehicles in the country, they are gradually separated from traditional high-voltage and high-current and traditional low-voltage automotive connectors.

Compared with traditional high-voltage and high-current connectors, the working conditions of new energy vehicle connectors are more complicated and changeable, and the reliability requirements of the connectors are higher; compared with traditional low-voltage automotive connectors, due to the increase in voltage level ( The current mainstream system voltage is higher than 300V DC), which increases the risk of human body injury from electric shock, and has higher requirements on the safety of the connector; therefore, the insulation and protection requirements of the product are improved compared with traditional low-voltage plug-ins.

The role of the connector for new energy vehicles is mainly to ensure the high-voltage interconnection system of the vehicle, that is, to build a bridge where the internal circuit is blocked or isolated to allow current to flow. The composition of the connector for new energy vehicles can generally be divided into three parts: auxiliary structures such as housing and sealing parts, insulating parts, and conductive contact pairs. Through the mating and mutual cooperation between the plug sheath and the socket sheath, the function of connection and conduction can be achieved.

The high-voltage connector is mainly used in the high-voltage and high-current circuit of new energy vehicles. It acts simultaneously with the conductive cable. It transmits the energy of the battery pack to various parts of the vehicle system through different electrical circuits, such as battery packs, motor controllers, and DCDC. Body power units such as converters and chargers.

The following figure is a layout diagram of the high-voltage connector in the application of the whole vehicle system.

What should be paid attention to in the design and selection of high-voltage connectors (top)?

The high-voltage electrical connection system mainly includes high-voltage wiring harnesses and connectors. The electrical connection system accounts for a certain proportion of the vehicle failure report, and the electrical connection has become a weaker link in the high-voltage system.

In the electrical connection system, the quality of the connector is particularly important, which has become a vital factor to ensure the safety and reliability of the electrical connection. When the connector is selected and applied, it needs to be based on the component’s use environment (such as temperature, humidity, altitude, etc.) and installation location (Vibration conditions, volume structure, sealing level requirements), current-carrying characteristics, cost accounting and other reasonable selection of products. The ideal expectation for high-voltage connectors is that the products have a higher level of safety protection, high temperature resistance, large current-carrying, low power consumption, grease resistance, small size, light weight, long life cycle and low cost.

1. Security

The safety protection of the connector mainly refers to the electrical performance meeting the design requirements, such as insulation, withstand voltage, electrical clearance, creepage distance, foolproof, and anti-finger (insulating material around the terminal, higher than the terminal height or the terminal with a plastic cap) design In addition to the above performance, it is necessary to pay attention to the connector HVIL, sealing protection, and EMC performance during application.

1) High Voltage Interlock

The high-voltage interlock uses electrical signals to confirm the integrity of the high-voltage system connection, and can also be used as a cover open detection.

When designing high-voltage connectors, consider the high-voltage safety protection during plugging and unplugging. For example, when disconnecting, the HVIL is disconnected first, and then the high-voltage terminals are disconnected; the opposite is true when connecting. HVIL connectors generally have a built-in type and an external type in structural design . Because the built-in type is compact and small in size, the built-in type is commonly used at present, and the high-voltage interlock circuit is installed between the high-voltage terminals.

In applications, some built-in connectors lack the CPA (Connector position assurance) of the interlocking device. If the connector structure is not well designed, under certain harsh conditions, some suppliers’ products will cause the displacement of the interlocking device. The discontinuity of the interlock signal brings unnecessary problems to vehicle debugging and safe driving.

EV High Voltage Connector 3 Pin Plug 35A Straight Metal Shield Plug 3.6mm HVIL Series

Figure 1 built-in type high-voltage interlock connector

In the actual use process, HVIL loop is mainly detected by signal (such as level, PWM signal) injection method, and the failure mode mainly considers HVIL circuit fault short-circuit (including short-circuit to power supply and ground. Level detection is used. The system may not be able to Risk of correct judgment) or disconnection (the product must ensure that the interlock device does not move).

In addition, the connector HVIL device contact resistance and wiring harness loop resistance should be considered when the connector is selected and designed to avoid HVIL detection failure due to signal voltage drop.

2) Protection level requirements

High-pressure connector sealing generally requires at least IP67, and even IP6K9K is required in the selection of some special occasions in the car to ensure that the use requirements are met even during high-pressure washing.

The current product protection requirements and verification methods mainly refer to GB4208, and the parts or connectors are placed at a depth of 1m in the water tank to detect whether the protection level IP67 is passed , but in actual use, whether this can simulate the performance of the vehicle The actual working conditions are debatable.

The actual working conditions of the vehicle need to experience fatigue loads and face the problem of material aging (see Figure 2). For example, long-term exposure to vibration conditions; extreme weather conditions, extreme cold and extreme heat; when wading, the water contains other impurities and needs to deal with corrosive conditions. In order to ensure the product performance throughout the life cycle, in actual use, it is important that the seal is good or bad when the vehicle is approaching the end of its life.


Figure 2  The-harsh-environment-of-the-vehicle

he water-dust and dust-proof test of the connector in the laboratory cannot fully simulate the actual environment of the vehicle connector. The connector product is tested for mechanical fatigue, vibration, thermal shock, salt spray, etc., and then tested for IP67, which can estimate the sealing performance of the system at the end of the life as completely as possible.

In addition, it is worth noting that the sealing material is generally made of rubber, which itself faces life degradation. At present, there is a lack of effective risk reports in the application of connector products. In the system design, it is also necessary to consider how to prevent problems caused by the life degradation of the sealing material.

If the sealing performance can be guaranteed during the whole life cycle of the product, the following points should be considered in the application design of the connector sealing: between the connector and the component (mainly involving the control of component structure design), between the connector and the cable (the product guarantees the seal The position of the ring does not move and the assembly accuracy is controlled during the production of the wiring harness), between the male and female ends of the connector (the product structure process and the integrity of the assembly).

3) EMC

As new energy vehicles use a large number of power electronic devices, the electromagnetic field generated by high voltage and large current will cause electromagnetic interference to other communication equipment, and the whole vehicle and parts must have the ability to resist interference and radiation.

When designing a high-voltage electrical connection system, the connector is required to have a 360°shielding layer and effectively connect to the cable shielding layer. The shielding layer covers the entire length of the connector to ensure sufficient shielding function and minimize the resistance between the shielding interfaces. During the product life cycle, the shield connection contact resistance is less than 10mΩ.

For high-voltage connectors made of plastic, the shielding must be realized with a metal surface.

What should be paid attention to in the design and selection of high-voltage connectors (below)?

Click to see what should be paid attention to in the design and selection of high-voltage connectors (top)

2. Connector temperature resistance and power consumption

If the connector (mainly the contact part) exceeds the specified operating temperature limit, the connector will reduce its safety characteristics due to heat, or even fail and be damaged. The main reasons for the increase in temperature of the connector are as follows:

1) Environmental factors, the layout position is easily affected by high temperature or is in a sealed cabin where heat is concentrated. If the layout position cannot be avoided, the temperature resistance of the connector should also be considered when selecting (such as Table 1).

standard Maximum operating temperature range Class level
Technical requirements for high-voltage and high-current wiring harnesses and connectors for electric vehicles -40℃~125℃ T3
SAE_USCAR_37 -40℃~175℃ T5
LV215 -40℃~150℃ /

Table 1 Connector operating temperature range

2) The connector heats itself, and the main influencing factors are heat dissipation of the contact resistance of the mating contact or poor crimping.

An important measure of the electrical performance of a connector is the contact resistance between the connectors. The smaller the contact resistance, the smaller the voltage drop, which means the lower the electrical loss, and the lower the temperature rise, and the higher the connection terminal Service life.

After the contact is heated, the plating layer will be affected, or an insulating film layer will be formed in the contact area, which will increase the contact resistance, further aggravate the temperature rise, and form a vicious circle.

If the connector is heated beyond the limit, the wiring harness will be burnt when the thermal failure is serious, and the insulating material will be chemically decomposed, which will reduce the insulation performance. In severe cases, the positive and negative poles of the connector may break down and short-circuit after the insulation material is thermally melted.

According to the Volkswagen VW80834 standard, the contact resistance of the connector cannot exceed the limit in Table2:

Cable cross-sectional area mm² Crimping resistance Contact resistance (total resistance, including crimp resistance)
Unused mΩ After aging mΩ Unused mΩ After aging mΩ
2.5 0.17 0.35 1.17 2.34
4.0 0.11 0.22 0.72 1.44
6.0 0.09 0.18 0.68 1.36
16 0.05 0.1 0.43 0.86
25 0.035 0.07 0.40 0.80
35 0.029 0.059 0.39 0.78
50 0.025 0.05 0.36 0.72

Table 2 Connector contact resistance range

After the connector cable is crimped completely, the contact resistance calculation formula is as follows:



Figure 1 Schematic diagram of connector contact resistance

a) Generally speaking, the crimping of the wiring harness is outsourced to the optional connector manufacturer, which can better guarantee the crimping reliability of the connector. In practical applications, the thermal failure of the connector is mostly due to poor crimping of the wire harness, such as insufficient crimping ratio, resulting in flash crimping, or excessive crimping ratio, resulting in incomplete crimping.

Cable cross-sectional area mm² Pulling force N
2.5 200
4.0 310
6.0 450
16 1500
25 1900
35 2300
50 2800
70 3400
95 4200

Table3 Crimp pull force strength requirements

b) The interface structure of the connector, such as the material/plating type and its purity, thickness, geometry, etc. determine the performance of the connector, including contact resistance, insertion force and insertion life.

The structure of the high-voltage connector terminal contact piece mainly includes split type, crown spring type, torsion spring type, strap type, etc. Different structural forms determine the electrical contact mode (surface contact, line contact and multi-point contact). ), which form to choose depends on the application of the connector. For frequently pluggable connectors, according to the principle of parallel shunting, the number of current-carrying bridges is used to achieve the purpose of reducing contact resistance.

Connector plating generally chooses silver with low contact resistance (as shown in Table 4). The thickness of the plating of different manufacturers’ products is different (the coating is too thin and wears badly, and the adhesion of too thick coating is insufficient). The selection should be based on different applicable occasions. Such as indoor/outdoor, frequent plugging and unplugging, etc.

For example, for charging connectors, the laboratory plug-in test can meet the goal of 10,000 times stipulated by the national standard. However, under the actual conditions of outdoor use, the first environmental conditions faced are worse than those of the laboratory (such as humidity, heat, dust, etc.); secondly, personnel operation Whether the specification is subject to random uncertainty. If used or maintained improperly, the local plating of the charging connector will be severely worn and “copper leakage” will occur, and copper rust will occur during use, resulting in a reduction in the effective current-carrying surface/point.

material Conductivity m/Ωmm² Resistivity Ωmm²/m
copper 57 0.017
tin 9 0.110
silver 62 0.016
gold 41 0.024
nickel 14 0.07

Table 4 Conductive properties of metal materials

In addition, in the application of connector selection, attention should be paid to the structure of the connector terminal. If the plug-in terminal is connected at a 90° right angle, the screw connection structure should be avoided. With this structure, the thread tooth pattern matching accuracy is very tight, but in the process of thread processing and wire harness assembly, incomplete connection and contact cannot be avoided. Especially for high-current terminal connections, in long-term use, the terminal thread teeth will be locally overheated, and the connector faces the risk of thermal failure.

Regarding this point, you can also refer to the VW80304-2013 standard formulated by Volkswagen, which stipulates that the cable outlet is 180°, 90°, and the right-angle 90° method does not allow threaded connection.

3. Connector life and cost

For connector performance and life requirements, the Volkswagen standard stipulates: Passenger car development projects must guarantee a full-featured life cycle: at least 15 years or 300,000Km (≥8000h action+30000h charging), and commercial vehicles must guarantee at least 15 years or 1000000Km.

In the connector selection process, product cost should not be the first consideration. Only on the basis of meeting performance requirements can it be possible to reduce costs and increase efficiency, unless it is willing to sacrifice the reliability of the vehicle’s high-voltage electrical connection.

Of course, in order to ensure product performance, excessive selection of structure and specifications should also be avoided in the selection, which will increase the cost of the product.

To sum up:

High-voltage electrical connection systems involve electrical architecture and safety, and connector products are related to the development of the entire industrial chain.

The performance of the product is determined by the structure and material of the product. After the product structure is optimized to the extreme, the competition of product performance is the competition between basic materials and physical research.

In product selection and application, if you do not grasp the interface material of the connector and understand the failure mechanism of the connector, it is impossible to scientifically evaluate the reliability of the connector.

Global standards for high-voltage connectors

Global standards for high-voltage connectors

In the International Standard Classification, high-voltage connectors relate to road vehicle devices, radiation measurement, electrical components, pipe components and pipes, floor treatment equipment, switchgear and controllers, mining equipment, transformers, reactors, inductors, road vehicle internal combustion engines, Nuclear energy engineering.

In the Chinese standard classification, high-voltage connectors relate to automotive electronics, electrical equipment and instrumentation, reactors, nuclear power plant safety power distribution equipment, hoses, tape, tape, household cleaning, whole containers, electronics, electrical equipment, high-voltage switchgear , Inductors, transformers, connectors, special equipment for coal mines, transformers, low-voltage power distribution appliances, intake and exhaust and fuel supply systems, general nuclear equipment.

The State Administration for Market Regulation and the National Standardization Administration of China, standards for high-voltage connectors

  • GB/T 37133-2018 Technical requirements for high-voltage and high-current wiring harnesses and connectors for electric vehicles

State Administration of Quality Supervision, Inspection and Quarantine, standards for high-voltage connectors

Standards on high-voltage connectors

  • SFS 2663-1975 Structure test of high voltage connector

German Institute for Standardization, standards for high-voltage connectors

  • DIN EN 1829-2-2012 High-pressure water spray machinery. Safety requirements. Part 2: Hoses, hose lines and connectors
  • DIN EN 62271-209-2008 High-voltage switchgear and controller. Part 209: Cable connectors for gas-insulated metal-enclosed switchgear with rated voltage higher than 52kV. Liquid-filled and extruded insulated cables. Liquid-filled and dry type Cable termination
  • DIN EN 1829-2-2008 High-pressure water spray machinery. Safety requirements. Part 2: Hoses, hose lines and connectors

American Society of Motor Vehicle Engineers, standards for high-voltage connectors

  • SAE/USCAR-37-2008 High voltage connector performance. Supplement to SAE/USCAR-2
  • SAE J 1949-1988 Road vehicle high pressure fuel injection pump end connector 60Deg female cone wheel

Canadian Standards Association, standards for high-voltage connectors

  • CSA C227.4-06 UPD 2-2007 Three-phase, gasketed distribution transformer with separable insulated high-voltage connectors
  • CSA C227.4-06 UPD 1-2007 Three-phase, gasketed distribution transformer with separable insulated high-voltage connectors
  • CSA C227.3-06-CAN/CSA UPD 1-2007 Low-section, single-phase, gasketed distribution transformer with separable insulated high-voltage connectors
  • CSA C227.4-06-2006 Three-phase, mated distribution transformer with separable insulated high-voltage connectors. 2nd edition
  • CSA C227.3-06-CAN/CSA-2006 Low-section, single-phase, gasketed distribution transformer with separable insulated high-voltage connectors. Fourth edition

European Committee for Electrotechnical Standardization, standards for high-voltage connectors

  • EN 62271-209-2007 High-voltage switchgear and control equipment. Part 209: Rated voltage>52kv gas isolation metal-encapsulated switch cable connector. Liquid-filled and extruded insulated cables. Liquid-filled and dry-type cable terminals

U.S. Defense Logistics Agency, standards for high-voltage connectors

  • DLA DSCC-DWG-89055 REV C-2006 No. 8 jack contact high voltage direct welding connector

Industry standards-coal, standards for high-voltage connectors

MT/T 947-2005 Flameproof high voltage cable connector for coal mine

American Institute of Electrical and Electronics Engineers, standards for high-voltage connectors

  • IEEE C57.12.23-2002 Underground, self-cooling single-phase distribution transformers with separable insulated high-voltage connectors: high-voltage 25000V and below, low-voltage 600V and below, 167kVA and smaller transformers
  • IEEE C57.12.23-1992 Underground type, self-cooling single-phase distribution transformer with separable insulated high-voltage connectors. High voltage (34,940GrdV/1400V) and below and low voltage (240/120V, 167kVA)
  • IEEE C57.12.26-1992 Separate self-cooling three-phase distribution transformer installed on the base used with separable insulated high-voltage connectors. (34500GrdV/19920V and below, 2500kVA and below)
  • IEEE 592-1990 Exposed semiconductor sheath of high-voltage cable joints and separable insulated connectors
  • IEEE N 42.4-1971 High voltage connectors for nuclear instruments
  • IEEE/ANSI N 42.4-1971 American National Standard for High Voltage Connectors for Nuclear Instruments

American National Standards Institute, standards for high-voltage connectors

  • ANSI C57.12.25-1990 Transformer. The interval type self-cooling single-phase distribution transformer installed on the base with detachable insulated high voltage connector. The high voltage is not more than 34500Y grounding/19920V, the low voltage is 240/120V, and the capacity is not greater than 167 kVA. Requirements

British Standards Institute, standards for high-voltage connectors

  • BS 6553-1984 Fuse Connector Selection Guide for High Voltage Fuses for Transformer Circuit Equipment

International Electrotechnical Commission, standards for high-voltage connectors

  • IEC 60498-1975 High voltage coaxial connectors for nuclear instruments


Design scheme of high voltage interlock

Definition of high voltage interlock:Check the integrity and continuity of the loop of the entire high-voltage system through the low-voltage signal, identify the abnormal disconnection of the loop, and disconnect the control electrical components of the high-voltage input in time.

Design scheme of high voltage interlock

  1. The HVIL circuit must be able to effectively, real-time and continuously monitor the on-off condition of the entire high-voltage circuit,
  2. All high-voltage connectors should be equipped with mechanical interlocking devices, and when the high-voltage connectors are disconnected, HVIL is disconnected first; when connected, HVIL is connected later.
  3. All high-voltage connectors cannot be connected or disconnected under non-human conditions
  4. The high-voltage interlock circuit should be equipped. Under special circumstances, the HVIL circuit can be directly detected through the BMS, and the high-voltage circuit can be directly disconnected.
  5. When an abnormality in the HVIL is recognized, the vehicle must give an alarm, such as instrument indicator lights, sound, light, etc. to remind the driver.

Design scheme of high voltage interlock

Scheme 1 is shown in Figure 1. The thick solid line represents the 12V low-voltage power circuit in the detection circuit, and the dashed line represents the HVIL monitoring circuit. The HVIL monitoring circuit of high-voltage components (DCDC, PTC, compressor, etc.) is controlled by VCU, and the low-voltage control output terminals of the three high-voltage relays in the battery pack are directly grounded through detection point 1 to monitor the working condition of the emergency power-off circuit. The high-voltage HVIL circuit of the motor and DCU is directly connected to the control coil of the low-voltage relay 2, and the other end is grounded.

Design scheme of high voltage interlock

Design scheme of high voltage interlock

Figure 1 Option One

working principle

When an emergency disconnection occurs, monitoring point 1 directly feeds back the detection result to the BMS, and the BMS disconnects three high-voltage relays. When the motor and the high-voltage connector of the DCU are connected, the low-voltage relay 2 is turned on, and the 12V of the BMS is turned on. When the high-voltage connector is not connected, the power of the BMS is disconnected through the low-voltage relay 2 to realize the power-off function. Other high-voltage components detect their respective HVIL states through detection points 3, 4, and 5, and feed them back to the VCU.

 Pros and cons

Each high-voltage component has its own HVIL test, if a fault occurs, it is easy to troubleshoot. The HVIL status of the motor and DCU can directly determine whether the BMS is working and reduce the risk. The disadvantage is that the low-voltage relay is added to control the BMS power supply, which makes the wiring harness design more complicated and the total weight of the wiring harness increases. In addition, if the low-voltage relay 2 is stuck, the VCU can only pass the BMS Indirectly disconnect high-voltage components.

In the second scheme (as shown in Figure 2), the thick solid line represents the 12V power line, and the dotted line represents the HVIL detection circuit. Compared with the first scheme, except for the motor and DCU, other high-voltage components are connected in series, and only one monitoring point is needed. In addition, the low voltage relay 2 is missing.

Design scheme of high voltage interlock

Design scheme of high voltage interlock

Figure 2 Scheme two

working principle

When encountering an emergency power failure, the detection point 1 sends the detection result directly to the BMS, and the BMS directly disconnects the high-voltage relay; the motor and DCU detect the connection of the high-voltage connector through the detection point 2 and send it to the VCU. If any connector is not properly connected, the VCU detection result controls the BMS, which makes the BMS control the high-voltage relay action to achieve power-off. The HVIL status of the other three high-voltage components is determined by monitoring point 3. If one is not connected, the VCU disconnects the high-voltage relay by controlling the BMS.

Pros and cons

Compared with solution one, solution two has advantages in wiring harness design and wiring harness quality, but if there is an abnormality in detection point 3, it is difficult to determine which high-voltage component has an abnormal HVIL.