The Composition and Application of EV HV Connecting cables

The layout requirements of EV HV high-voltage wiring harnesses, including position, fixation and size, involve the structure of the cable, but mainly the layout, which may be helpful for the application part. The structure of the high-voltage cable is described in detail, including conductors, shielding layers, insulation layers, и т. д., which should directly answer the composition question. The application part mentions the power transmission from battery to motor, инвертор, и т. д., as well as signal transmission, which is also critical.

High-voltage connecting device, which mentions the voltage level of high-voltage cables, shielded and unshielded types, and the difference between single-core and multi-core, which are all composition details. The application aspect mentions the power transmission between electrical devices, such as the main drive motor, air conditioning system, и т. д., which needs to be combined with these contents. The composition of the high-voltage wiring harness is briefly described, including connectors, terminals, wires, и т. д., which may supplement the information of the components.

High-voltage components, which mentions that high-voltage cables connect battery packs, chargers and other components, emphasizes insulation and withstand voltage, and this application part needs to be cited. The wiring harness between the fast charging port and the high-voltage box uses high-voltage cables, and this part of the application scenario should also be considered.

The Composition and Application of EV HV Connecting cables

The components of EV HV Connecting cables should include conductor material (copper or aluminum), conductor shielding layer, insulation layer, insulation shielding layer, metal shielding layer, and protective cover. The application aspects involve power transmission (battery to motor, инвертор, и т. д.), charging system (fast charging/slow charging), auxiliary system (air conditioning, PTC heater), EMC design, и т. д..

1. Composition of high-voltage connecting cables for electric vehicles
High-voltage cables are the core components of electric energy transmission in electric vehicles. Their structural design must meet the requirements of high voltage, high current and electromagnetic compatibility. They mainly include the following levels:

‌Conductor‌
Copper (excellent conductivity) or aluminum (lightweight and low cost) is used as the core material, responsible for current transmission‌.
‌Conductor shielding layer‌
Wrap the conductor for uniform electric field distribution and prevent partial discharge‌.
‌Insulation layer‌
High-voltage materials (such as cross-linked polyethylene) are used to provide electrical insulation protection to prevent leakage or short circuit‌.
‌Insulation shielding layer‌
Further optimizes the electric field distribution and reduces the damage of electrical stress to the cable‌.
‌Metal shielding layer‌
Made of copper braid or aluminum foil, it suppresses electromagnetic interference (EMI) and improves electromagnetic compatibility (EMC)‌.
‌Protective cover‌
The outer protective structure has the characteristics of wear resistance, high temperature resistance, corrosion resistance, и т. д., and is suitable for complex working conditions‌.

‌Special design type‌:
‌Shielded cable‌: Reduce electromagnetic interference through the metal shielding layer, suitable for scenes with high EMC requirements‌.
‌Unshielded cable‌: Used in low-interference environments, lower cost‌.
‌Single-core/multi-core cable‌: Single-core cable is suitable for high current transmission (such as motor power supply), and multi-core cable is used for multi-signal composite transmission‌.

2. Application of high-voltage connecting cables for electric vehicles
High-voltage cables are used for power transmission and signal control in the high-voltage system of the whole vehicle. The main application scenarios include:

‌Power system power transmission‌
Connect the power battery with the drive motor, инвертор, DC/DC converter and other components to transmit 200-1500V high-voltage DC or AC.

High current density requirements must be met (such as symmetrical arrangement of the three-phase line of the motor).

‌Charging system‌
‌Fast charging interface‌: Connect the fast charging port with the high-voltage power distribution box (PDU) to support high-power DC charging.

‌Slow charging interface‌: Connect the on-board charger (OBC) with the battery pack to transmit AC.

‌High-voltage auxiliary system‌
Provide power for air-conditioning compressors, PTC heaters, electric steering/brake systems, и т. д..

‌Electromagnetic compatibility optimization‌
Shielded cables are used in key paths (such as battery to motor lines) to reduce the impact of electromagnetic interference on other electronic equipment.

3. Typical technical requirements
‌Voltage level‌: AC 600V/DC 900V or AC 1000V/DC 1500V, matching according to component requirements, power battery, drive motor, и т. д..
‌Fixed spacing‌: ≤300mm when the cross-sectional area is greater than 16 mm²; ≤200mm when ≤16 mm², avoid hanging or excessive bending, wiring harness fixing and layout
‌Safety spacing‌: The gap with the stationary parts is ≥10mm, avoiding collision deformation areas (such as anti-collision beams, car doors)‌

Traditional new energy vehicle wiring harnesses are composed of wires and plastic wire troughs. Because plastic trunking has poor heat dissipation, high-voltage wire bundles require larger gauge wires to reduce the impact of heat. In addition, changing and developing a new wire trough protection mold design is costly and the production cycle is long. So we saw the tube shielding wire harness solution, the representative of which is Sumitomo high-voltage wire harness.
With the rapid development of new energy vehicles in recent years. Its high-voltage electrical components, such as motors, inverters and high-voltage batteries, are also constantly developed and improved. The high-voltage wiring harnesses connecting them are also constantly developing and improving. The vehicle is in urgent need of high-voltage wiring harnesses to reduce costs, weight and layout space.

Figure 1 shows the timeline for mass production of high-voltage wire harness products. In 1999, our company began large-scale production of high-voltage wiring harness products for Honda INSIGHT. The first comprehensive development of high-voltage wiring harness parts, such as wires, terminals and connectors, began in 2001 for the Toyota ESTIMA hybrid vehicle. In terms of terminals, two types of bolt-type molded and plug-type connectors have been developed based on the technical requirements of the connection interface. Electromagnetic shielding started with individually shielded cables, then introduced integral braided wire harness shielding for the Toyota Prius in 2003, and introduced the first tube shielding technology for the Honda CIVICHYBRID in 2005. The maximum temperature requirement for high-voltage wire harnesses has also changed from the original 120°C to 150°C.

Figure 2 shows the application of high-voltage wiring harness products in HEV models. On the right, the wiring harness assembly is shown, secured using wire troughs. In the lower left corner is the motor wiring harness. The terminals are bolted and shielded overall.

In order to prevent high-voltage wiring harnesses from causing interference to low-voltage wiring harnesses, radios, и т. д., electromagnetic shielding is particularly important for high-voltage wiring harnesses. In addition, most of the high-voltage wiring harnesses of new energy vehicles are routed on the chassis, and mechanical protection performance is also particularly important for high-voltage wiring harnesses.
The left side of Figure 3 shows the individually shielded high-voltage wire harness. Each wire is covered with a copper braided shield, with the overall shielding scheme on the right. There is no separate braided shield outside the cable, but overall shielding on the outside of multiple high-voltage cables. А 2003 Toyota Prius used an overall shielded high-voltage wire harness design to simplify the wire harness structure and reduce the number of necessary components, thereby reducing the cost of the overall high-voltage wire harness system. Figure 4 shows the use of protective sleeves and injection molded wire troughs on the outside of the two design options for mechanical protection.

The disadvantages of the above high-voltage wiring harness design scheme are as follows:
1. Low thermal conductivity: due to low thermal conductivity caused by protective sleeves and injection molded wire troughs, the axial thermal conductivity of the wire harness is low;
2. As a result of this low heat transfer, the size of the wires increases, resulting in an increase in the weight and cost of the high-voltage harness;
3. Mechanical protection structure (wire trough): If the layout of the high-voltage wire harness changes, the shape and structure of the wire trough also need to be changed, which increases the cost and lengthens the development cycle.
In order to eliminate these shortcomings, YAXUN developed a tubular shielded high-voltage wire harness, which installs unshielded high-voltage wire harnesses into aluminum alloy tubes. Aluminum alloy steel pipe effectively combines electromagnetic shielding and mechanical protection, as shown in Figure 5.

Compared with the previously mentioned solutions of individual shielding and overall shielding using protective sleeves and injection molded wire ducts, it has the following advantages:
1. The high heat transfer of aluminum alloy materials can reduce the conductor specifications of the wire harness;
2. Reduce the weight of the overall high-voltage wiring harness system;
3. The arrangement and installation of high-voltage wire harnesses are easier and more flexible.
This solution has been used in Honda INSIGHT (2009), CR-Z and Fit Hybrid (2010), and FREED Hybrid (2011).
Through experiments, the heat dissipation capabilities of high-voltage wire harnesses protected by aluminum alloy tubes and those protected by standard polypropylene plastic tubes were compared. Experiments have shown that aluminum alloy pipes have better heat dissipation capabilities than standard polypropylene plastic pipes.
The test setup is shown in Figure 6. Both components are placed on top of a heating system that generates high temperatures of approximately 350°C. Figure 7 shows the measured surface temperature measurements. Aluminum alloy tubes have good thermal conductivity and their axial heat transfer performance is much better than plastic protectors.

This excellent heat dissipation performance can reduce the conductor specifications of high-voltage cables and reduce the temperature resistance level of the cables. These two aspects can effectively reduce the cost of high-voltage cables.
In addition, due to this design, the high-voltage cable is changed from a shielded cable to an unshielded cable, eliminating the need for the cable outer sheath and injection molded protective trunking, and the weight can be reduced by about 18%. As high-voltage cables are changed from shielded cables to unshielded cables, the design of high-voltage connectors becomes simpler.

Since aluminum alloy steel pipes have good formability, high-voltage wire harnesses using aluminum alloy steel pipes are more conducive to installation during manufacturing.

The high-voltage wire harness using aluminum alloy steel pipe has good rigidity and does not sag, and the distance between its fixed points can be set farther. Due to its high flexibility, it is difficult to ensure the ground clearance of traditional high-voltage wire harnesses when placed on the chassis.

When the design of high-voltage wire harnesses using injection molded wire ducts is changed, the mold needs to be re-opened or the mold needs to be modified. The use of aluminum alloy steel pipes only requires bending, which greatly shortens the development cycle of high-voltage wire harnesses.

Another most important performance is the electromagnetic shielding performance. Figure 16 Test method for electromagnetic shielding performance.

Judging from the test results, the 0.8MHz individually shielded cable high-voltage wire harness has better shielding performance. Higher than 0.8MHz, high-voltage wire harnesses using aluminum alloy pipes have better electromagnetic shielding performance.

Because aluminum alloy steel pipes are used and arranged under the chassis of the vehicle, anti-corrosion performance testing is essential. Figure 18 shows that the pipeline after the gravel impact test and the wiring harness assembly after the salt spray test meet the requirements of the salt spray test.

‌Summary‌: Electric vehicle high-voltage cables achieve safe and efficient power transmission through a multi-layer structure, and their applications cover power, charging and auxiliary systems. Their selection needs to comprehensively consider voltage levels, electromagnetic compatibility and mechanical protection requirements to ensure the reliability and safety of the vehicle’s high-voltage system‌.