First and foremost, the materials used in the terminal blocks play a crucial role in their overall quality. The insulation housing should be made of flame-retardant engineering plastic, while the conductive components should be made of copper alloy materials. This is because the plastic insulation material and the conductive components directly influence the quality of the terminal block, determining its insulation and conductivity functions.

In addition, the production process of the terminal blocks is also critical. If the production process is not up to standard, the thread processing is not done properly, and the torque is not within specifications, the terminal block will lose its ability to connect wires effectively.

Furthermore, the appearance of the terminal blocks is also important. A high-quality terminal block should not only meet the functional requirements, but also have a visually appealing appearance. A well-designed terminal block can make a positive impression on users and enhance the overall user experience.

In conclusion, when it comes to high-quality terminal blocks, it is essential to consider the materials used, the production process, and the overall design of the product in order to ensure optimal performance and reliability.

When using PCB terminal blocks for wiring applications, it is important to keep in mind the following precautions:

1. Always ensure that the power is switched off before starting any wiring operations. Never attempt to work on the terminal blocks while they are live. If you are unsure whether the power is off, use a voltage tester to verify. Additionally, if there are sliding buttons on the terminal blocks or switches, it is advisable to replace them if they are worn out to prevent any risk of electric shock.

2. When connecting to the power source, make sure to install PVC conduit for wire routing. Avoid leaving wires hanging loosely without any proper support or fixation on support brackets or busbars.

3. Pay attention to the length of the wires when connecting to the switch box. It is recommended to keep the wire lengths within a suitable range and properly route them through conduits. Avoid pushing the wires directly into the switches for fixing.

By following these precautions, you can ensure safe and efficient operation of the PCB terminal blocks. If you have any further questions or need assistance, please feel free to contact us.

High voltage wire harness is an important carrier of the power and signal transmission and distribution system of new energy vehicles, and the crimping performance of high voltage wire harness terminals is the most important performance index of new energy vehicles. This paper establishes a data analysis model for the crimping performance of high voltage wire harness terminals of new energy vehicles, and finds out the best adaptation range of the compression ratio of high voltage wire harness terminals by analyzing relevant data, so as to improve the process capability and quality level of high voltage wire harness cold crimping.

With the rapid advancement of the country's new energy automobile industry, it has brought major opportunities to the development of new energy wiring harnesses. The difference between high-voltage wire harness and low-voltage wire harness terminals is that high-voltage terminals tend to generate heat due to the large current passing through them, which leads to the decrease of terminal mechanical strength and wire harness insulation performance, and causes conductor oxidation to further aggravate heat and other problems. High voltage terminal crimping needs to consider not only the reliability of crimping, but also the low temperature rise at the crimping area. This paper mainly studies the effect of cold crimping on terminal temperature rise.

 

01 Crimp type

High voltage terminals are commonly connected by crimping, resistance welding, and high frequency welding. Crimping equipment and dies are used to connect wires and terminals together through a crimping process. High-frequency welding is the use of high-frequency welding machine wire and terminal welding together. Resistance welding is the use of special resistance welding equipment to connect wires and terminals together.

This paper mainly analyzes the performance of crimping. The advantages of ordinary crimping: simple operation, easy use and maintenance, low manufacturing cost, high operational efficiency, suitable for mass production. Disadvantages: The wiring harness and terminals that require high current pass rate and small resistance after the connector requires the wire and terminal to be connected cannot be met.

The common crimping mode of the large square high voltage terminal is shown in Figure 1, which is a hexagonal closed terminal. The advantages of ordinary crimping are obvious, but it is particularly important to minimize the resistance of ordinary crimping. Reducing resistance means reducing heat, reducing product temperature rise, and making product life and quality better.

 

 

 

02 terminal heating hazards

After the terminal is heated, it is easy to oxidize itself and the contact surface of the conductor, forming an oxide film, which increases the contact resistance, and the increasing speed increases exponentially with the increase of temperature, further increasing the temperature rise speed of the terminal, which will cause a fire in serious cases. At the same time, the elastic element of the contact structure will be annealed, the contact pressure will be reduced, and the contact resistance will be further increased. In addition, the heat will make the insulation layer of the wire connecting the terminal aging brittle, causing the insulation performance to decline, there is a risk of leakage overheating caused by fire.

 

03 Heat source of terminal

As shown in Figure 2, the high voltage harness has three heat sources.

3.1 Conductor

The conductor itself has resistance, the smaller the cross-sectional area, the higher the resistance, and the resistance will cause heating.

3.2 Terminal crimping

If the compression ratio is not enough, the conductor will be loose, resulting in large resistance and easy heating. Excessive crimping is easy to cause the cross-sectional area to become smaller, and the carrying current is not enough to cause heat.

3.3 Contact of male and female terminals

The terminal contact is poor, or the contact surface of the terminal is oxidized, resulting in serious heating.

 

04 Method to reduce the terminal temperature

4.1 Reduce contact resistance

(1) Materials with low resistivity are used. Commonly used high-voltage terminals are H62, H65 copper, or high-conductivity copper. For products larger than 125 A, it is recommended to use high-conductivity copper with low resistivity.

(2) Reduce the contact resistance of the conductor. Compact the terminal and conductor as much as possible to reduce the crimping resistance.

(3) Increase the cross-sectional area of the conductor, increase the cross-sectional area, and reduce the temperature rise of the wire.

4.2 Increase the heating area of the conductor

(1) Forced cooling, air cooling, water cooling and other measures can be used.

(2) Reasonable arrangement of conductors, wiring harnesses with large current, as far as possible arranged in a space that is easy to dissipate heat, conducive to natural heat dissipation.

 

05 Effect of crimping on temperature rise

For crimping, refer to the 4.2.6 voltage drop test requirements in QC/T 29106-2014 "Automotive Wiring Harness Technical Conditions" [1] and the temperature rise test requirements in GB/T 20234.1-2015 "Connection Devices for conductive Charging of electric vehicles Part 1 General Requirements" for verification. The process is shown in FIG. 3 and FIG. 4. The obtained data are shown in Table 1.

 

5.1 Compression ratio/Compression ratio calculation method

(1) Refer to VW60330-2013 standard

Where, Acrimp is the cross-sectional area of the conductor contained in the crimp; Aconductor is the nominal cross-sectional area of the conductor.

(2) Refer to SAE/ USCAR21-2014 standards

Where, T is the area retained when the crimp blade is closed; At is the cross-sectional area of the nominal terminal; Ac is the cross-sectional area of the nominal conductor.

(3) The difference between conductor compression ratio and terminal compression ratio

According to VW 60330-2013 [4] standard, the calculation of compression ratio only includes the compression of the conductor without the terminal, which can directly reflect whether the conductor has a gap. When the compression ratio is less than 100%, there should be no gap. We can call it the wire compression ratio.

According to the SAE/ USCAR21-2014 standard, the calculation of the compression ratio includes the compression of the conductor and the terminal, which cannot directly reflect whether there is a gap in the conductor, but can directly reflect the real cross-sectional area of the compression joint. In order to facilitate data comparison, this article defines the terminal compression ratio =100T/ (At+Ac).

Both calculation methods have their own advantages.

 

5.2 Analysis Results

(1) As shown in Table 1, when the conductor compression ratio of product 3# reaches 104%, the pulling force has reached the standard of 50 mm2 stipulated in QC/T 29106-2014, and the conductor pulling force is ≥2 700 N, but at this time, the compression joint has not been fully compacted, and there are large safety risks. Therefore, the tension of the high voltage terminal can not be used as a standard to judge the quality.

(2) The resistance value in the table is not completely corresponding to the temperature rise trend, which should be caused by the difference in the contact resistance of the terminal individual and the inconsistency caused by the oxidation of the terminal coating. However, from the general trend, it basically conforms to the corresponding relationship of lower resistance and lower temperature.

(3) The compression ratio of the 7# terminal is 73%, and there is an oxide layer on the surface of the conductor and the terminal, which will gradually be destroyed with the reduction of the compression ratio value. When the compression ratio of the terminal is 73%, the oxide layer of the conductor begins to collapse, which makes the copper wire fuse more tightly and the temperature rise is slightly reduced, indicating that the terminal compression comparison is appropriate at this time.

(4) From the point of view of temperature rise value fluctuation, the impact of crimping on temperature rise can reach 10 ℃. This has a greater impact on the crimping of high voltage terminals.

(5) 10# Product terminal compression ratio At 60%, the theoretical cross-sectional area of the conductor at the terminal crimp is only 30 mm2, according to SAE/ USCAR21-2014 terminal compression ratio calculation, the cross-sectional area at the crimp in addition to the conductor, the cross-sectional area of the terminal should also be included. The actual cross-sectional area between the crimped conductor and the terminal is 66.97 mm2, which is greater than the nominal cross-sectional area of the conductor of 50 mm2. Therefore, the compression ratio does not cause a bottleneck at the compression area, and is in line with the actual situation. In addition, the calculation method of the terminal compression ratio is more suitable for high-voltage terminals.

(6) Too low compression ratio will cause the temperature rise at the crimp joint to be too high. According to the actual measurement, when the terminal compression ratio reaches below 40%, the terminal crimp resistance will gradually increase. The terminal temperature rise began to rise slightly.

(7) Terminal compression ratio analysis for hexagonal crimp terminals. First of all, no matter what the cross-sectional area of the pressure junction should not be less than the nominal conductor cross-sectional area; Secondly, due to the material thickness selection of each high-voltage terminal will be different, according to the terminal compression ratio =100T/(At+Ac), some terminals have a low At cross-sectional area, after compression, too low terminal compression ratio will cause the cross-sectional area of the crimp is less than the nominal conductor cross-sectional area. Therefore, the cross-sectional area after crimping needs to be as large as possible. In addition, if the compression ratio is too low, the mechanical tension value of the terminal will decrease, which will affect the reliability of the terminal crimping.

 

06 Conclusion

Based on the above analysis, consider the reliability of terminal crimping strength and terminal resistance. The actual terminal compression ratio is controlled at 65% ~ 75%, and the conductor compression ratio is 65% ~ 80%. In addition, from the experimental data, some of the resistance and temperature rise data fluctuations are related to the coating and oxidation of the terminal and the contact structure of the terminal, so it is not enough to reduce the temperature rise from the perspective of crimping quality alone. It is necessary to pay special attention to the daily preservation of the terminals, the quality of the coating of the terminals, and the life of the terminals, the insertion force, and the contact area.

For products with large temperature rise, it is recommended to use high-frequency welding, which makes copper heat through friction at ultra-high frequencies, melting copper and bonding, which has lower resistance, so it has a better effect in controlling temperature rise.

Aichie Tech provides auto wiring harness , high voltage ev cable assembly and low -voltage auto wiring harness around the world. It has introduced new production equipment, which greatly improves the quality and efficiency of production. Customers are widely distributed in Europe and North America. Production employees and experienced engineering teams and sales teams serve our customers; please contact us now! We will provide you with competitive prices!

E: sales03@aichie.com

WeChat: 180 2750 2150

Tel: +86 180 2750 2150

At present, the competition in the new energy vehicle market is becoming increasingly fierce. With Tesla's price reduction, BYD's open letter asking suppliers to reduce prices and other events, it can be expected that the subsequent competition will enter a more heated stage.

If automobile companies want to win a place in the highly competitive new energy vehicle market, they can only rely on high-quality products with high added value and leading technology. While the major car companies continue to promote technological innovation, they also focus on the optimization of parts costs in order to enhance product strength and enhance the competitiveness of enterprises. Among them, high-voltage wiring harnesses, as highly valuable components in pure electric vehicles, naturally become the key to cost optimization.

1. Introduction to high voltage wiring harness

The high voltage wiring harness connects the various components of the high voltage system, as the medium of high voltage power transmission, and is the main carrier of power output on the electric vehicle, mainly used for transmitting electric energy and shielding external signal interference.

High voltage harness has the characteristics of high voltage, high current, high protection level and anti-electromagnetic interference, which is the neural network of pure electric vehicle high voltage system, and is the key component of vehicle performance and safety.

High voltage wiring harnesses of pure electric vehicles are generally divided into power battery high voltage wiring harnesses, motor controller high voltage wiring harnesses, fast charging socket wiring harnesses, slow charging socket wiring harnesses, air conditioning system wiring harnesses and charging high voltage wiring harnesses, among which charging high voltage wiring harnesses are the wiring harnesses connecting high voltage distribution boxes to vehicle chargers, air conditioning compressors and power battery pack heaters.

The high-voltage wire harness mainly consists of high-voltage connectors, high-voltage cables, cladding materials (tape, heat shrink pipe, bellows, wear-resistant self-winding pipe, etc.), and protection plates. The production process of high voltage wire harness mainly includes cutting wire, preassembly of accessories, terminal crimping/ultrasonic welding, shielding crimping, wire harness assembly and electrical inspection.

2. Cost composition of high voltage wiring harness

The cost of high voltage wiring harness consists of material cost, processing fee, packaging and transportation fee and management fee.

The material cost of high voltage wiring harness is mainly determined by the technical scheme of wiring harness, and the processing cost includes labor cost, power cost, equipment depreciation cost and low value consumable goods.

The following is the cost composition ratio of the high-voltage wiring harness of a certain vehicle (see Figure 1) and the cost composition ratio of the high-voltage wiring harness material (see Figure 2). The cost of the high-voltage wiring harness material accounts for about 73.8% of the total cost of the wiring harness. It is necessary to reduce the cost of high voltage wiring harness by optimizing design and production process.

Figure 1 Proportion of the cost composition of high voltage wiring harness	Figure 2. Material cost composition ratio of high voltage wiring harness

 

3 High voltage wire harness cost reduction research

There are three main methods to reduce the cost of enterprises in the automotive industry, including scale, supplier collaboration and technology cost reduction, among which technology cost reduction is the most effective and sustainable way to reduce costs.

At present, there are three main methods of cost reduction: cost benchmarking, management technology and technical means.

Under normal circumstances, the method of technical means includes reducing redundant functions, improving the localization rate and standardizing the platform.

In the pure electric vehicle high voltage wiring harness cost reduction activities, this research mainly uses technical means to optimize the cost of high voltage wiring harness from the following aspects.

3.1 High-voltage system architecture optimization

On pure electric vehicles, High-voltage components include power battery, 3-in-1 (motor controller + drive motor + subtraction), PDU (high-voltage distribution box), ECP (electric compressor), 2-in-1 (IPS=OBC+DC-DC), HVH (battery heating), PTC (occupant heating), slow charger (ACInlet), and fast charger (DC) Inlet, high pressure harness, etc. These components constitute the high pressure system of the vehicle. The high voltage system architecture of pure electric vehicles is optimized, which can greatly reduce the number of connectors used and redundant high voltage wiring harnesses. Taking the high voltage system architecture optimization of a project as an example, before optimization, PDUs in the high voltage wiring harness system architecture only exist as power distribution function modules, and there is no vehicle functional performance related module, as shown in Figure 3.

FIG. 3 Architecture diagram of high voltage system before optimization

The independence of PDUs increases the number of transfers in HV wiring harness systems. The two functions of HVH and PTC are similar, resulting in an increase in the number of high-voltage harness circuits. The fast and slow charging sockets are arranged on the left and right rear side, and are too far away from the electrical interface (the battery fast charging interface is in the front, and the charger slow charging interface is in the front cabin), so that the high voltage wiring harness length is too long.

After research and analysis, the functional electrical components are only used for connecting the function of copper bar and power protection function of the fuse, and it is easy to integrate with other electrical appliances. The PDU and IPU integration can eliminate a high voltage distribution box assembly, while saving a set of motor controller wiring harnesses (approximately 1.5m of 50mm2 wire and two pairs of φ8mm terminal connectors), which can bring significant cost reduction. HVH and PTC have similar functions, and when the two functions are combined, the high-voltage wiring harness can reduce one loop (about 1.5m of 3mm2 wire and two pairs of 2.8mm blade width terminal connectors), and the high-voltage system architecture is optimized, as shown in Figure 4.

FIG. 4 Architecture diagram of high voltage system after optimization

Through this high voltage system architecture optimization, four high voltage connectors and two high voltage wiring harnesses are reduced, and the cost of high voltage wiring harnesses can be reduced by about 730 yuan.

3.2 Optimization of high-voltage wiring harness layout

The high-voltage wiring harness layout needs to be continuously optimized according to the model, and the use of high-voltage cables can be reduced after optimization to further reduce costs. Taking the layout optimization of the fast and slow charging ports of a certain vehicle as an example, before optimization, the fast and slow charging ports were arranged in the left and right rear side, and the length of the fast and slow charging harnesses was too long, among which the length of the slow charging harnesses was about 4.5m and the length of the fast charging harnesses was about 4m, resulting in high cost of the fast and slow charging high-voltage harnesses. After optimization, the charging port is arranged at the left and right sub-boards, close to the charger and battery pack, to reduce the length of high voltage wiring harness. The layout diagram before and after optimization is shown in Figure 5 and 6. The cost can be reduced by about 260 yuan through this high-voltage wiring harness layout optimization.

Figure 5 Layout diagram of fast and slow charging before optimization

Figure 6 Layout diagram of fast and slow charging after optimization

3.3 High voltage harness material optimization

High voltage wire harness cost composition, material cost accounted for the highest, the current status of the analysis, the current high voltage wire harness material optimization direction mainly for charging socket integrated design, high voltage connector localization, high voltage cable diameter optimization and material one-to-many optional optimization.

3.4 Integrated design optimization of charging socket

Before optimization, the charging socket is designed as a split type with high cost. Before optimization, the split type charging socket is shown in Figure 7, including a fast charging socket and a slow charging socket. Through the development and design of the charging socket according to the platform scheme, the main structure of the charging socket of all projects is solidified to minimize the development cost. After optimization, the integrated charging socket is shown in Figure 8. Through this optimization, a set of flange molds can be reduced and the high voltage wiring harness assembly cost can be reduced by about 8 yuan.

Figure 7 Split charging socket before optimization

Figure 8 Integrated charging socket after optimization

3.5 High voltage connector localization

In recent years, the high voltage connector industry has developed rapidly, and a number of excellent domestic high voltage connector brand suppliers have emerged. Before optimization, the main use of TE and other foreign brands of high-voltage connectors, through the localization of high-voltage connectors continuous optimization, with domestic brands such as Luxshare, Ebusbar and other localization replacement, the cost reduction of high-voltage connectors is of great significance, as shown in Table 1 below for the high-voltage connector localization demonstration case.

Table 1 High-voltage connector localization demonstration case

Original Brand	Original P/N	Equivalent Brand	Equivalent P/N
TE	1-2347299-1	Ebusbar	123-0500-0002
TE	2-2356258-2	Luxshare	HVP800022CVA11

3.6 High voltage cable diameter optimization

Through the interpretation of regulations, benchmarking and statistical cloud big data measures to optimize the cable diameter of high voltage lines. For specific high-voltage cables, it is often possible to optimize the section, temperature requirements, flexibility and shielding effect to avoid excessive size and excessive components. Taking fast-charging high-voltage cables as an example, the optimized front-line cable diameter is 70mm2, and the optimized cable diameter is 50mm2, which can meet the actual charging requirements.

3.7 One-to-many optional optimization of materials

The one-to-many high-voltage wiring harness materials can fully mobilize the enthusiasm of tier1 suppliers and make use of tier1 suppliers' own supply chain advantages to choose the best cost plan for supply. Taking high-voltage cables with relatively high material costs as an example, the current main specifications of high-voltage cables are developed according to the one-to-many idea according to the high-voltage cable standard, and each specification harness factory has multiple specifications to choose from, of which the specific application wire of each loop needs to be confirmed according to the actual load of the vehicle. Through continuous optimization design, many materials can be selected one-to-many at present, and Table 2 below is only a one-to-many example of some materials.

Table 2 One-to-many examples of materials

Materials	Supplier	P/N
50mm² Silicone shielded wire	Kolop	FHLR2GCB2G_50
	Hua Cheng	FHLR2GCB2G_50
	Lenny	FHLR2GCB2G_50
	Beijing Fox	FHLR2GCB2G_50

3.8 Platform and standardized design

The platform and standardized design from the whole vehicle wiring harness principle and raw materials can greatly shorten the development cycle of the whole vehicle wiring harness design stage, reduce repeated verification tests, and reduce the wiring harness cost. Through the continuous platforming and standardization of wire harness materials, the types of materials are reduced, and the quantity of a single material can play a large-scale effect, which is of great significance for material cost reduction. Through research and analysis, the platform and standardization of secondary materials (connectors, cables, accessories, etc.) can greatly reduce the material cost of high voltage wire harness. The following is an example of the high voltage plug-in platform. Under the condition of the same electrical performance, the plate end connectors of different brands (TE and Luxshare) can be installed in the opening size of the aluminum alloy panel of the battery pack at the same time, as shown in Figure 9, 10 and 11. This platform design has strong versatility.

Figure 9 Holes on the aluminum alloy panel of the battery pack

Figure 10 Board end of TE brand HVP2P800

Figure 11 HVP2P800 board end of Luxshare brand

4. Summary and prospect

Due to the characteristics of high voltage, high current and large number of wire diameters, high voltage wire harnesses of pure electric vehicles are faced with challenges such as wiring, safety, shielding, weight and cost. As a high-value pure electric vehicle component, high voltage wire harness can contribute to the cost reduction of the whole vehicle through continuous cost optimization research. Cost reduction work is a continuous optimization and continuous activity, and the follow-up needs to be continuously optimized to minimize the cost of the vehicle and provide customers with more competitive products.

 

Aichie Tech provides auto wiring harness , high voltage ev cable assembly and low -voltage auto wiring harness around the world. It has introduced new production equipment, which greatly improves the quality and efficiency of production. Customers are widely distributed in Europe and North America. Production employees and experienced engineering teams and sales teams serve our customers; please contact us now! We will provide you with competitive prices!

E: sales03@aichie.com

WeChat: 180 2750 2150

 

 Tel: +86 180 2750 2150

Wire harnesses, sometimes called cable assemblies or cable harnesses, are used in every corner of the electronics industry, including consumer appliances, commercial equipment, robotics and industrial systems, computers and servers, telecommunications equipment, medical systems, aerospace platforms, and of course trucks and cars. However, the wiring harnesses used in electric vehicles (EVs) are the most complex and demanding.

 

This may come as a bit of a surprise, as drivetrain components in electric vehicles (EVs) are simpler than those in internal combustion engine (ICE) cars. Two factors that contribute to the complexity of EV cable harnesses are the use of high voltages in the drivetrain and the fact that all controls in the EV communicate via the harnesses; There are no hydraulic or mechanical linkages commonly found in ICE vehicles.

 

 

HV cable harness

The complexity of electric vehicle harnesses begins with multiple high-voltage (HV) domains. The HV domain includes motor wiring harnesses, battery pack wiring harnesses, and separate wiring harnesses for fast charging and regenerative braking. Each of these HV wiring harnesses must be designed to handle large currents efficiently.

In addition to effectively carrying large currents and providing insulation for high voltages, these harnesses must also deal with high temperatures and high temperature rises. This requires large wire diameters, high voltage connectors, and cable protection.

Cable protection comes in many forms. Cables, especially motor drive cables, are screened to control the generation of electromagnetic interference that can interfere with the operation of other vehicle systems.

To protect people who may come into contact with the vehicle, federal safety standards require all electric vehicle manufacturers to use orange housings on any HV cables outside of a physical electrical protective barrier (Figure 1). Depending on the cable being protected, the covering can be braided tube, textile or other tape, bellows, etc.

 

It's not just HV

The harnesses in the HV domain are also subject to high currents to provide the high power levels needed for EV drivetrains and fast battery charging. Power levels of tens or even hundreds of kilowatts are common. Even with large diameter cables, IR losses can be large and produce a corresponding temperature rise.

 

The basic EV operating environment includes temperatures up to +125°C. Under some high load conditions, the surface temperature of the HV harness can reach +150°C.

 

 

Wire Diameter and Bending Radius

One way to reduce the temperature rise caused by IR losses is to use a larger diameter cable. Larger wires, with lower resistance, generally have better thermal characteristics and can emit more heat, further reducing temperature rise under high loads.

 

The trade-off is that larger wires have larger minimum bending radii, which makes HV harness formation and wiring more difficult. If the recommended minimum bending radius is exceeded, the insulation, shielding, or conductor may be permanently damaged. The wire diameter also directly affects the selection of HV connectors.

 

 

High voltage connector

 HV connector is an important component in HV harness design. The high-voltage connectors in electric vehicle wiring harnesses must combine high electrical performance, mechanical strength, and the ability to withstand high levels of shock and vibration and exposure to harsh environments. Some considerations include:

 

IP68 protection class

The insulation resistance must be at least 500MΩ for 1 kVdc

High voltage interlocking mechanism

Shielded connection with HV cable to ensure high EMI performance

Chemical resistant housing material

How to confirm the new energy vehicle high voltage wire diameter?

 

Influencing factors of wire diameter

1.Transmission capacity: Simply put, it is the amount of electricity that the cable needs to transport. The greater the transmission power, the larger the wire diameter required, which is like to transport more water, you must use a thicker water pipe.

2. Allowable voltage drop: When electrical energy is transmitted in the wire, the voltage will drop to a certain extent. The allowable voltage drop in the industry is clearly defined, and in order to meet this standard, the cable diameter must be adjusted according to the cable length and transmission power. In general, the longer the cable, the smaller the voltage drop allowed, and the larger the required cable diameter.

3.Ambient temperature: Temperature has a significant effect on the resistance of the wire. As the temperature increases, the wire resistance increases. In high temperature environment, in order to ensure the normal operation of the wire, it is necessary to appropriately increase the diameter of the wire.

4.Electromagnetic compatibility requirements: there are many electronic devices inside new energy vehicles, and electromagnetic interference generated by high-voltage wiring harnesses can not affect the normal operation of other equipment. Thicker wires can reduce the current density and reduce electromagnetic radiation, so the choice of wire diameter will also be affected when meeting electromagnetic compatibility standards. For example, in high-voltage harnesses close to sensitive electronic components such as on-board computers, larger wire diameters may be required to ensure electromagnetic compatibility.

5.Space layout limitation: the interior space of the car is limited, and the high-voltage wiring harness needs to be rationally arranged in the limited space. This requires that when determining the wire diameter, both the electrical performance should be satisfied and the spatial adaptation should be considered. If the wire diameter is too large, it may not be possible to route in the narrow gap of auto parts, affecting the vehicle assembly.

 

 

Basic requirements and information input

The High Voltage Cable shall comply with the requirements specified in SAE J1654 (High Voltage Primary Cable) and SAE J1673. On this basis, it is necessary to combine the following factors to determine the diameter selection of high-voltage wire cable.

1). Wire diameter selection should meet LV216-1/2, ISO19642 and other standards.

2). Determine the load characteristics of the electrical components to which the high voltage cable harness is connected, including steady-state current strength, voltage requirements, transient conditions and current strength and current waveform (smooth, pulse, frequency, etc.).

3). The cross-sectional area of the conductor is determined according to the steady-state current intensity

4). Adjust the cross-sectional area of the conductor according to the working environment temperature

The operating temperature of the high-voltage wire cable is -40℃~125℃, and it needs to pass the voltage resistance test of AC2500V/min and 50Hz.

If the layout environment of the high-voltage conductor exceeds the allowable operating temperature of the conductor, the conductor with a larger cross-sectional area must be selected. When the ambient temperature is up to 180 ° C, the cross-sectional area of the conductor should be increased by one step. When the ambient temperature is up to 250 ° C, the cross-sectional area of the conductor increases by two levels.

 

Figure: External high voltage wiring harness and assembly connection schematic diagram

 

Method and procedure of determining wire diameter

3.1 Method 1, use the product specification to determine

• Check the working voltage platform of the high-voltage wire, the current general voltage platform is below 1000V DC, so the high-voltage wire resistant to 1000V DC is more used;
• Select the wire diameter according to the temperature rise curve combined with the carrying capacity of the wire and the working environment temperature;
• Comparing the peak current, peak duration and wire smoke curve (see figure below), the peak duration is less than the wire smoke time;
• Comparing the fuse time with the wire smoke time, the wire smoke time is longer than the fuse time.
• After the above steps to initially determine the wire diameter, combined with the high-voltage plug-in model and specifications, to confirm whether the wire can be applied, especially the need to check the high-voltage plug-in on both sides of the wire to meet its requirements.

 

Figure 1:35 square silica gel cables in the flow temperature rise and smoke curve

 

3.2 Method 2, calculation formula of wire diameter selection

The current intensity and cross-sectional area are calculated as follows:

• The current intensity of the electrical equipment is: I=P/U.

          *P is the load power, *U is the rated voltage

•  The cross-sectional area of the conductor is calculated as follows: A=IρL/UVL.

          *A is the cross section of the wire, *I is the current value, *ρ is the resistivity of the copper wire (0.0172Ω · m at standard atmospheric                pressure and room temperature), *L is the length of the wire, *UVL is the allowable voltage drop of the wire

• Current density S=I/A. Check the current density to avoid excessive heating of the wire.

          *I is the current intensity and *A is the cross section of the wire

Current density is a very important concept in the field of electricity, and it plays a key role in determining the diameter of a high-voltage cable. The current density refers to the size of the current passing through a unit area, which reflects the distribution of the current across the cross section of the conductor in amperes per square meter.

The value of current density will be affected by the service life of the cable, load nature and electricity price. For example, for cables with long-term operation and stable load, lower current density values can be selected to reduce cable losses and operating costs; For cables with short-term use or large load fluctuations, the current density value can be appropriately increased to reduce the initial investment cost.

The current density of high-voltage wiring harnesses of new energy vehicles is relatively special, and the current density of general copper wires is 3-6A /mm². This is because the car space is limited, there are strict requirements on the size of the wire, and it is necessary to minimize the volume and weight of the wire harness under the premise of ensuring electrical performance and electromagnetic compatibility. However, in some high-power fast charge or high-performance drive motor harness, in order to meet the demand for instantaneous large current, the current density upper limit may be close to or even exceed 6 A/mm² for a short time, but this requires more advanced heat dissipation and electromagnetic shielding measures to ensure the normal operation of the wiring harness.

 

Examples

When the maximum current is 150A, the high voltage harness of 35mm² is used at 125 ° C; At 180℃, 50mm² wiring harness is selected; At 250 ° C, use a 70mm² high voltage harness.

 

Determining the diameter of high voltage wire is a work with high technical content, which needs to consider many factors. I hope that through today's sharing, you can have a deeper understanding of this field. If you encounter related problems in actual work or have wire, wire harness needs, welcome to Email us: sales03@aichie.com, we will try our best to help you solve the problem!

 

Supplement, confirm the type of wire

Conductor type	Material characteristics	advantage	shortcoming	Applicable environment	Special requirements
Silicone conductor	Soft, good temperature resistance	Soft, good temperature resistance	Poor tear resistance and oil resistance	1. The operating temperature is greater than 150 ° C 2. The wiring harness layout space is small, the complete radius does not meet the 5D area, or the flexibility of the wiring harness is strictly required 3. High voltage harness protection is better, no oil no wear area	The high voltage plug-in has clear requirements for use
Cross-linked polyolefin wires	Hard material	Good wear resistance and tear resistance, low cost	Poor softness, poor temperature resistance	1. The working environment temperature is not more than 150℃ 2. The wiring harness layout space is large, the bending radius is <5D, or the wiring harness assembly is not difficult 3. The wiring harness may have oil contact, or wear vibration amplitude is large	The high voltage plug-in has clear requirements for use
Other wires	-	Can meet different special needs	-	-	1. There are flame retardant requirements, HB or V0 grade wires can be selected. 2. There are shielding requirements, unshielded wires, single shielded wires, double shielded wires can be selected, and the shielding density is generally above 85%

The environment is more complicated when the wiring harness is routed outside the car. In order to better protect the wires, it is necessary to use reasonable coverings outside the wires to protect the wear. The coverings can play a role in prevention, early warning, earthquake, early warning, etc., so that the wires can be used normally in the environment. This article mainly introduces the selection of high-voltage wiring harness coverings. The following is the main text.

Types and characteristics of high-voltage wiring harness coverings

The main high-voltage wiring harness coverings include corrugated tubes, sleeves, wear-resistant tapes and thermal insulation sleeves. In the selection of high-voltage wiring harness coverings, corrugated tubes, sleeves and wear-resistant tapes are transparent choices.

1.1 Corrugated tubes

Corrugated tubes are almost widely used in high-voltage wiring harness protection. Generally, high-voltage wiring harness coverings can be round tubes, and the color is orange. In addition to the common round corrugated tubes, there are also elliptical corrugated tubes, which are suitable for the situation of multi-line common corrugated tubes.

 

There is a specific formula for selecting the diameter of the corrugated pipe, that is, the diameter of the corrugated pipe = the outer diameter of the conduit / 0.92 (for multi-strand wires, the outer diameter of the wire is the outer common tangent circle diameter).

Generally speaking, it is best to use a closed-end corrugated pipe for the corrugated pipe, and the difference between the inner diameter of the corrugated pipe and the outer diameter of the cable is ≤5mm; for heights below 300mm, an open corrugated pipe can be used, and the two ends and the middle of the open corrugated pipe are wrapped with PVC tape.

For example:

A high-voltage wire cable is 50mm², and the outer line of the wire is 13.97mm, which matches its corrugated pipe.

For a single-core wire corrugated pipe, the diameter of the corrugated pipe used is = 13.97/0.92 = 15.18mm, so the corrugated pipe should be selected with an inner diameter greater than 15.18mm and close to the inner diameter. For example, a corrugated pipe with an inner diameter of 16.00/15.37mm.

1.2 Sleeves

The sleeves can effectively prevent harness fatigue. Compared with bellows, the sleeves have higher wear resistance and smaller outer diameter, but the cost will be different.

 

The sleeves should be orange in color. There are open self-rolling and closed types. The open self-rolling type is easy to install. When choosing the open self-rolling type, it should be noted that the overlap rate of the curling should reach 30% (range). The specific overlap rate of the curling needs to be determined with the corresponding supplier.

1.3 Wear-resistant tape

Compared with bellows and sleeves, wear-resistant tapes are easy to use, increase the outer dimensions of the harness to the smallest, and hardly affect the outer dimensions of the harness. The cost is higher. However, it is rarely used under normal circumstances and is suitable for situations where the environment requirements are not high, such as in the cable trough, inside the equipment end, etc.

 

1.4 Heat insulation

Manhattan can effectively protect the weather forecast of the high-voltage harness and ensure the normal operation of the harness. Excessive temperature will affect the normal operation of the high-voltage harness. To avoid such situations, an early warning should be used when the harness is located in a high temperature area.

 

If the wiring is near the three-way catalytic converter or parallel to the exhaust pipe and the gap is less than 100mm, thermal insulation protection must be done.

Common heat sources include exhaust pipes, EGR exhaust gas recirculation valves, oxygen sensors, three-way catalytic converters, etc.

 

Comparative analysis of the wear resistance and cost of wiring harness covers

 

As mentioned above, in the selection of high-voltage wiring harness covers, bellows, sleeves and wear-resistant tapes are common choices. Below we use this transparent cover to compare the wear resistance and cost to provide a reference for the selection of high-voltage wiring harness covers.

 

2.1 Wear resistance comparison

1.Wear-resistant tape: Compared with bellows and sleeves, wear-resistant tape has the lowest wear resistance. It is rarely used under normal circumstances and can be used in situations where the environment requirements are not high, such as in the wire slot and inside the equipment end.

2.Bellows: Generally, high-voltage wiring harnesses can use bellows, which have wear resistance and wear tiles. Corrugated tubes are widely used in wire harness protection. In addition to the common circular corrugated tubes, there are also elliptical corrugated tubes, which are suitable for the situation where multiple wires share the same corrugated tube.

3.Sleeve: The sleeve has the highest wear resistance. Compared with the groove tube, it can more effectively prevent the wear of the wire harness. The sleeve is divided into open self-rolling and closed. For the open self-rolling installation, the overlap rate of the curling edge should reach 30% (range). The specific overlap rate of the curling edge needs to be determined with the corresponding supplier.

2.2 Cost comparison

1. Abrasion-resistant tape: The lowest cost. Because it is easy to use, the added wire harness size is the smallest, and it hardly affects the wire harness size, so it is an economical choice in some environmental conditions where the requirements are not high.

2. Corrugated tube: The cost is moderate. The price of the corrugated tube is affected by many factors, such as material cost, production process and technology, market competition, etc. Generally speaking, the price of mid-range corrugated tubes is around 200-500 yuan/meter.

3. Sleeve: The highest cost. Although the sleeve has higher wear resistance and smaller outer diameter, the cost is relatively high.

In summary, in the selection of high-voltage wire harness covers, the appropriate cover should be selected according to the specific working environment and needs.

• If the working environment requirements are not high, wear-resistant tape can be selected;·
• If better wear resistance and moderate cost are required, corrugated tube can be used;
• If the wear resistance is extremely high and cost factors are not considered, sleeves can be used.

 

At the same time, other factors such as installation convenience and appearance requirements can be combined for comprehensive consideration to ensure that the high-voltage wire harness is effectively protected in different environments.

 

Key points of high-voltage wire harness cover options

3.1 Consider the working environment

When selecting high-voltage wire harness covers, factors such as working environment, space size and special functions need to be fully considered.

The temperature requirements of different parts of the vehicle are different, which requires the design of the high-voltage wire harness to be adjusted according to the specific temperature conditions to ensure normal operation in various environments. The working temperature of the high-voltage wire harness refers to the temperature range within which the product can work stably for a long time and maintain normal characteristics.

Near the internal combustion engine with the highest temperature and increased vibration, PA or PP corrugated tubes with good flame retardancy, corrosion resistance and good mechanical properties are ideal choices. After the high-voltage wire harness is wrapped with a corrugated tube, the outer periphery should also be wrapped with PVC tape for sealing to ensure better protection.

For different working environments, covers with different characteristics need to be selected. If the working environment temperature is high and the gap between the high-voltage wire harness and the heat source is less than 100mm, the initialization bracket is necessary.

3.2 Consider the appearance color of the cover

The appearance color of the high-voltage wire harness is usually orange.

This color has a specific purpose of selection. On the one hand, it can serve as a warning to remind people to pay attention to the existence of the high-voltage wire harness and avoid accidental touch; in addition, the uniform color can also quickly identify the high-voltage wire harness during vehicle maintenance and inspection.

 

Summary

In addition to mastering the type and characteristics of the cover, the selection of high-voltage wire harness covers also requires in-depth understanding of the working environment of the wire harness layout area, such as the working environment temperature, wear resistance requirements, etc. Only by combining the working environment's demand for coverings with the characteristics of the covering product itself can the selection of coverings be made properly.

With the deep integration of the new generation of information and communication, new energy, new materials and other technologies with the automotive industry, the "new four modernizations" of the automotive industry - electrification, intelligence, networking, sharing - are leading the development trend of the industry. In this context, the field of wire harnesses will develop in five directions: lightweight, high-voltage, high-speed, platform-based and intelligent.

Automobile wiring harness is the main body of automobile circuit network, and there is no automobile circuit without wiring harness. Automotive wiring harness is mainly composed of wire, connector (connector), protective cover, buckle and so on. The wire is the carrier of the transmission of current, the connector is used to connect different wires and electrical equipment, the protective sleeve can protect the wire from wear and the influence of the external environment, the buckle is used to fix the position of the wire harness. The components of the car wiring harness work together to ensure the normal operation of the car circuit.

 

Composition of automotive wiring harness

1. Lightweight

1.1 Optimize the architecture and reduce the length of the wire harness

With the transformation of the vehicle network architecture from the traditional distributed architecture to the centralized domain architecture, the harness length is reduced by 50% compared to the traditional vehicle. This optimization not only reduces the weight of the wiring harness, but also reduces the material cost and assembly difficulty.

1.2 Application of new products such as aluminum wire and copper-clad aluminum alloy wire

Aluminum wire because of its density and price is 1/3 of copper, electrical conductivity is 64% of copper, by raising the wire specification 1-2 grades, can achieve replacement, conductor part 50% light, wire cost can be reduced by 40%. Large diameter aluminum wires have been used in batch power lines, and small diameter copper-clad aluminum alloy wires can directly replace the same diameter copper wires, applied in low-voltage wiring harness assembly, the cost of wires can be reduced by 10%.

1.3 Miniaturization of wires and connectors

The signal line can be replaced by a 0.22/0.13/0.08mm² ultra-thin wire, which has been widely used in the joint venture brand. Miniaturized terminals and connectors help reduce the overall size and weight of the harness.

1.4 Research and application of FFC flexible flat cable

Flexible Flat Cable (FFC) Flexible flat cable (FFC) Because of its thin, flexible, flexible and folding advantages, flexible flat cable is widely used in positions with high space requirements, such as ceiling cable harnesses and low-voltage cable harnesses in power battery packs.

1.5 Research and application of electronic fuse box

By replacing traditional fuses and relays with semiconductor chips, the volume of electronic fuse boxes is reduced by about 15%, the weight is reduced by about 20%, and it has the advantages of high reliability, programmable and maintenance-free.

 

Automotive electrical architecture development trend

2. High-pressure

2.1 Platform design of high voltage connectors

The high voltage system of new energy vehicles usually uses high voltage and high current above 300V, which has higher safety requirements for insulation and protection of connectors. High voltage connector platform design key items include temperature rise and derating curve, high voltage interlock design, protection level, electromagnetic shielding, connector material selection, etc.

2.2 Chip connector

The chip connector has a unique advantage in the field of high current, its contact points are linear, and the contact resistance can be reduced by increasing the width of the contact or arranging multiple contacts side by side.

2.3 High current Busbar

In order to achieve the goal of fast charging, Busbar came into being and can realize automatic assembly, which saves the process of drawing, annealing and twisting compared to cable forming.

2.4 High-voltage harness EMC performance development

High voltage wiring harness to solve the EMC three elements of the "road", using ground filtering and shielding; The high-voltage wire adopts double-layer shielding, and the high-voltage connector adopts shielding ring, shielding spring and other schemes.

 

High voltage connector development trend

3. Speed up

3.1 Research and application of vehicle Ethernet

In-vehicle Ethernet is a new LAN technology that uses Ethernet to connect the electronic unit in the car, which is mainly used in systems with high bandwidth requirements, such as automatic driving assistance systems (ADAS), in-vehicle diagnostic systems (OBD) and in-vehicle infotainment systems, etc., which can achieve data transmission rates of 100M/s or even 10G/s.

3.2 Special cables and special connectors

The diversity of high-frequency signals on the car brings the diversity of special wire types, such as FM/AM feeders, USB conversion cables, GPS antennas, TBOX antennas, camera cables, fakra coaxial lines, HSD video cables, Ethernet cables, etc. Special wire has the characteristics of high reliability, low electromagnetic radiation, low power consumption, low delay and synchronous real-time technology.

 

Automotive network development trend

4. Platform design

4.1 Configuring Platformization

Set up basic configurations by configuring combination packages and cover all configurations with the least amount of wiring harness state.

4.2 Principles Platform

The vehicle architecture is divided into subsystems with different functions, and each subsystem gradually realizes the principle platform.

4.3 Interface platformization

Coordinate the interface information of all electrical parts of the vehicle, and establish a database according to the interface solidification of the component end and the wiring harness end.

4.4 Layout Platforming

The wiring harness is divided into different modules according to the vehicle area, and the wiring harness 3D platform-based layout architecture is established according to the platform-based layout principle.

 

Principle of different sectional layout scheme

5. Intelligence

5.1 Modular design of wiring harness

Wiring harness modular design can be divided into different modules, according to the module development, can quickly achieve the diversification of wiring harness production, to achieve a car line, different vehicles, to meet the individual needs of customers.

5.2 Automation of production line

The promotion of flexible intelligent automated production lines is a strong support for Made in China 2025 and Industry 4.0, and the more important significance is to improve product consistency, improve enterprise production efficiency, and enhance industry competitiveness.

 

Wiring harness modular design and production

Through these detailed technical introduction and development trend analysis, we can see that the automotive wiring harness industry is developing rapidly in the direction of lightweight, high-voltage, high-speed, platform-based, and intelligent, in order to meet the "new four modernizations" needs of the automotive industry.