Views: 0 Author: Site Editor Publish Time: 2025-05-19 Origin: Site
The automotive high-voltage wiring harness (high-voltage cable and high-voltage interface) is a key component of the high-voltage electrical system, which ensures the reliable operation and safety of electric vehicles. The development and design of the vehicle high-voltage wiring harness mainly involves cable layout, cable diameter selection, high-voltage connector selection, charging cable and interface type and application, cable fixing and protection, etc.
According to the layout of the high-voltage components of electric vehicles, the high-voltage connection harnesses between various high-voltage components such as battery to PDU, motor controller to motor, AC/DC charging, etc. are reasonably arranged.
If the high-voltage harness needs to pass through the sharp edge of the hole, a corresponding protective structure should be designed. In the early stage of vehicle development, the layout of the harness must be kept away from heat and vibration sources as much as possible, otherwise a sufficient distance should be maintained. The high-voltage harness has a large outer diameter and a large weight. To avoid stress concentration, the minimum bending radius of the cable should generally be greater than 5 times the wire diameter.
In order to reasonably distribute the load, it is necessary to increase the support for fixed installation. When the harness is arranged in a straight line, the spacing between the fixed points is ≤300mm; when the curve is arranged, the fixed points are fixed at both ends of the arc. The spacing between the fixed point and the connector is ≤150mm to withstand the deadweight and vibration load of the harness.
The fixing device must use automotive-grade cable ties, insulating brackets, etc. The drive motor harness must consider the influence of component movement and vibration. The harness size design should be reasonable to meet the stress distribution along the length direction and avoid harness accumulation due to excessive length. For harness movement, add rubber ring buffers and guide groove fixing structures to avoid cutting the harness and other components and causing harness damage.
Following points should be considered when arranging the wiring harness:
Considering the EMC electromagnetic interference factor, shielded high-voltage cables should be used to avoid high-frequency noise emission. High and low voltage cables must be arranged separately to avoid mutual interference caused by overlapping wiring harnesses.
Considering the aesthetics of the wiring harness layout, its direction must be consistent with the direction of related components to avoid oblique layout. For the departure cabin wiring harness, it should be routed under or inside the structural parts or components as much as possible, and the exposed high-voltage wiring harness bottom of the vehicle should be shielded and protected by tubular protective covers and shielding plates.
Considering that the installation and maintenance parts of the connector are the same, different connector specifications and positioning methods are selected to prevent misplugging. A certain plug-in margin must be left at the end of the connector.
Consider high voltage safety. This high voltage has exceeded the safety voltage of the human body. The body cannot be the same as the low-voltage system of the tractor, and a double-track system must be used.
Selection of high-voltage cable
The selection of cable diameter depends on the layout of each high-voltage electrical component of the vehicle to distinguish the main circuit from the branch circuit. And determine the response characteristics of the high-voltage components connected to the high-voltage wiring harness.
Characteristics include operating voltage, rated power, peak power, rated current, peak current, duration, etc. Operating temperature and ambient temperature also affect the wire diameter of the cable. Since high current transmission leads to high power consumption and the temperature rise of related components will also increase, the design of high-voltage cables must be able to withstand higher temperatures. If the cable is laid in an environment that exceeds the allowable operating temperature of the cable, a cable with a larger cross-sectional area must be selected.
When Tmax is up to 180℃, the cross-sectional area of one conductor will be used. 250℃ Tmax is the cross-sectional area of two conductors. Cable structure High-voltage cables are divided into single-core cables and multi-core cables. The cross-sectional area of high-voltage cables is circular and the sheath color is orange. Multi-core cables are composed of multiple single-core conductors. Single-core cables must also meet the relevant technical parameters of single-core cables. If multi-core cables are used for signal transmission, use a separate shielding layer to ensure that the signal is not lost.
The conductor mainly uses multi-core soft copper stranded wire to meet the technical requirements of wire internal resistance, soft bending, etc. The insulation layer must be resistant to high and low temperatures, flame retardant, and mostly composite structure. To meet EMC protection requirements, the inner sheath of the high-voltage cable with shielding layer is woven with bare copper wire or copper-plated wire, and the braiding density is ≥90%.
Electrical performance: It is necessary to consider the relevant electrical performance parameters such as rated working voltage, rated working current, insulation resistance, withstand voltage level, shielding and interlocking.
Environmental performance: It is necessary to consider the requirements such as working temperature, ambient temperature, salt spray level, flame retardant level, resistance to solution reagents and prohibited substances.
Mechanical performance: Test the vibration resistance and corresponding mechanical life according to different working conditions.
Safety performance: High-voltage interlocking is divided into built-in and external types. The built-in type has a compact layout and a small size. The built-in type is used in electric vehicles, and the high-voltage interlocking is detected by controllers such as VMS or BMS. To ensure personal safety, after the high-voltage connector is separated, the live part must drop below 60Vd.c and 30Va.c within 1S.
Maintenance switch MSD, or manual maintenance switch, is a key component to ensure the high-voltage electrical safety of pure electric vehicles. It is an actuator to achieve electrical isolation of the high-voltage system at critical moments. It highly integrates the circuit breaker and fuse, and is equipped with a suitable fuse to protect the circuit from overcurrent and short circuit. The correct design and operation of the maintenance switch plays a vital role in the electrical safety of electric vehicles.
Charging interfaces are currently divided into two types: AC and DC. The AC interface connects the AC grid power supply to the on-board charger through the control protection device on the cable. The DC interface is a power supply device that directly controls the conduction of the electric vehicle battery.
The rated voltage of the AC interface is 250Va.c or 440Va.c, and the rated current does not exceed 63A. The rated voltage of the DC interface is 750Vd.c or 1000Vd.c, and the rated current does not exceed 250A. The rated voltage and current values of the charging interface are determined according to the vehicle layout requirements. Other relevant electrical characteristics and other AC and DC charging interface parameters must comply with the requirements of national standards GBT20234.2-2015 and GBT20234.3-2015.
There are many ways to fix the wire harness. Please choose the fixing method of the wire harness or connector according to the layout of the high-voltage equipment of the whole vehicle. The commonly used fastening and fixing methods include one-piece fixing tie with wedge-shaped fixing head, one-piece fixing tie with cedar-shaped fixing head, etc., which are suitable for round hole fixing.
One-piece welding stud fixing tie, double U-shaped tie with welding stud fixing isolation, etc., are suitable for welding stud fixing. Fixing tie and snap-on assembly are suitable for fixing pipes, hoses, wire harnesses, etc.
Plate edge clips are suitable for fixing metal or plate edges with a thickness of no more than 3mm. Heavy-duty fixers are suitable for wires with a wire diameter of ≥35mm². Cable duct brackets are suitable for lifting cables from the frame longitudinal beams, isolating cables from protruding body parts, and preventing cable wear. Connector clips are suitable for fixing high-voltage connectors. Corrugated pipe clips are suitable for quickly fixing corrugated pipes.
Bellows protection: Closed bellows are used, which are characterized by wear resistance, flame retardancy, and heat resistance. The temperature range of the bellows is -40 to 150°C, and can reach 200°C for a short time. The common materials on the market are PA (nylon), PE (polyethylene), and PP (polypropylene), each of which has its own advantages in flame retardancy, wear resistance, and bending fatigue resistance. The color of the bellows must be orange to distinguish the low-voltage wiring harness of the whole vehicle. Rubber sheath plastic sealing, PVC tape wrapping, cable fixed sealing and other measures are adopted.
Pipe sleeve protection: For wiring harnesses arranged in a small space or special parts, special pipe sleeves are required for shielding protection. Universal pipe sleeves have the characteristics of stable chemical properties, no aging, and strong corrosion resistance.
Guard plate protection: For the protection method of high-voltage wiring harnesses (total positive and negative poles of the battery) arranged in the chassis, the design of the guard plate should consider factors such as waterproofing, sand splashing, and cutting resistance. Most of the guard plates are made of ABS+PC material, which has the characteristics of impact resistance, high temperature resistance, low temperature resistance, and flame retardancy.
Sheath protection: Due to the use of winding sheath, it can be used in areas that are easily damaged or impacted. It is characterized by high temperature resistance, impact resistance, cut resistance, light weight, and easy installation.
Tape protection: Tape is used in various applications of wire harnesses, and is often used for protection, bundling, insulation, flame retardancy, marking and other functions. High-voltage wire harnesses use flame-retardant PVC tape, which can withstand high temperatures of 80°C.
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