Automotive high-voltage wiring harness (high-voltage cables and high-voltage interfaces) is a key component of the high-voltage electrical system, providing reliable operation and safety of electric vehicles. The main development and design solutions for the whole vehicle high-voltage harness involve cable layout, cable diameter selection, high-voltage connector selection, charging cable and interface types and applications, cable fixing and protection, etc.
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The high voltage connection harnesses between each high voltage component, such as a battery to PDU, motor controller to the motor, AC/DC charging, etc., are reasonably arranged by the layout position of the high voltage components of the electric vehicle.
Electric Vehicle High Voltage Components Layout DiagramIf the high-voltage wire harness needs to pass through the sharp edge of the hole, should design the corresponding protection structure. In the early full vehicle development, harness arrangement must try to avoid the heat source vibration source; otherwise, it should be kept at a sufficient distance. High-voltage wire harnesses have a large outside diameter and weight. To avoid the concentration of stress, the minimum bending radius of the cable is generally greater than the diameter of the wire diameter of 5 times.
To reasonably distribute the load, the need to increase the support of the fixed installation. Wire harness straight line arrangement between fixed points ' 300mm; over the bend arrangement, fixed points are fixed at the two endpoints of the arc. Fixed point and connector spacing ' 150mm to withstand the weight of the harness and vibration load.
The fixing device must use automotive-grade ties and insulated brackets, etc. The drive motor harness must consider the effects of component movement and vibration. The harness size has to be reasonably designed to meet the stresses distributed in length and avoid harness buildup due to excessive length. For the wire harness movement, increase the rubber ring cushion and guide slot fixed structure to avoid cutting the wire harness and other components, resulting in damage to the wire harness.
The following points should be considered during the wiring harness arrangement
Considering EMC electromagnetic interference factors, shielded high-voltage cables are used to avoid high-frequency noise emission. High and low-voltage cables must be arranged separately to avoid mutual interference caused by cross-overlapping harnesses.
Considering the aesthetics of the harness arrangement, the direction needs to be consistent with the direction of the dependent parts to avoid oblique direction. For the hair cabin wiring harness, as far as possible in the structural parts or components below or inside the alignment, the bottom of the entire vehicle's exposed high-voltage wiring harness uses pipe guards and a shielding plate for shielding protection.
Consider installing and maintaining the same part of the connector to prevent misinsertion by choosing a different specification and positioning method for the connector. The end of the connector needs to leave a certain amount of margin for plugging.
Consider high-voltage safety. This high-voltage electricity has exceeded the human body's safety voltage. The body can not be the same as the low-voltage system of the hitch. It must use a dual-track system.
The cable diameter is according to the layout of each high-voltage electrical component of the vehicle to distinguish the main circuit and branch circuit. And to determine the response characteristics of the high-voltage components connected to the high-voltage wiring harness.
Internal Structure of High Voltage CableCharacteristics include operating voltage, rated power, peak power, rated current, peak current, duration, etc. Operating temperature and ambient temperature also affect the cable diameter. Since high current transmission can lead to high power consumption and related components to increase the temperature rise, thus the high-voltage cable design must withstand higher temperatures. If the cable is arranged in an environment that exceeds the allowable operating temperature of the cable, a cable with a larger cross-sectional area must be selected.
For Tmax up to 180', the conductor cross-sectional area will be used in one block. 250' Tmax is the conductor cross-sectional area used in two blocks. Cable structure High-voltage cables are divided into single-core cables and multi-core cables. High-voltage cables are round in cross-section and have an orange sheath color. Multi-core cables are made up of multiple single-core wires. Single-core cables must also meet the relevant technical parameters of single-core cables. And if the multi-core cable is used for signal transmission, please use a separate shield to ensure the signal is not lost.
The conductor mainly uses multi-core soft copper-stranded wire to meet the technical requirements of the wire's internal resistance and soft bending degree. The insulation layer must resist high and low temperatures and flame retardant, mostly composite structure. For EMC protection, the high-voltage cable with a shielding layer uses bare copper or copper-plated wire braided on the inner sheath layer with a braiding density of ' 90%.
Electrical performance: we need to consider the rated working voltage, rated working current, insulation resistance, voltage withstanding grade, shielding and interlocking, and other related electrical performance parameters.
Environmental performance: we need to consider the requirements of operating temperature, ambient temperature, salt spray level, flame retardant level, and resistance to solution reagents and banned substances.
Mechanical performance: according to different working conditions to test the vibration resistance and the corresponding mechanical life.
Safety performance: high voltage interlock has the built-in type and external type. The built-in type has a compact layout and small size. The built-in type is used on electric vehicles and detects high-voltage interlocks by controllers such as VMS or BMS. To ensure personal safety, the charged part must be reduced to below 60Vd.c and 30Va.c within 1S after separating the high-voltage connector.
Automotive Connectors MSDAutomotive Connectors MINI MSDThe maintenance switch MSD, or manual maintenance switch, is a key component to ensure the high-voltage electrical safety of pure electric vehicles and is an actuating component that can achieve electrical isolation of the high-voltage system at critical moments. It can integrate both the breaking device and the fuse to a high degree. The appropriate fuse is configured internally to protect the circuit from overcurrent and short circuit protection. Proper design and operation of the maintenance switch play a vital role in the electrical safety of electric vehicles.
The charging interface is currently two kinds: AC and DC. The AC interface connects the AC grid power to the vehicle charger through the control and protection device on the cable. The DC interface is a power supply device with a direct control guidance function to the electric vehicle battery.
AC interface rated voltage 250Va.c or 440Va.c, rated current not exceeding 63A. DC interface rated voltage 750Vd.c or Vd.c, rated current not exceeding 250A. The rated voltage and current value of the charging interface are determined according to the requirements of the vehicle layout. Other relevant electrical characteristics and other AC/DC charging interface parameters must meet the requirements of national standards GBT.2- and GBT.3-.
There are various ways to fix the wire harness. According to the arrangement of each high-voltage device of the whole car, reasonably choose how to fix the wire harness or connector. The commonly used tight fixing methods currently include one-piece fixing ties with wedge-shaped fixing heads, ones with cedar-shaped fixing heads, etc., applicable to the round hole way fixing.
One-piece welding stud fixing tie, with welding stud fixing piece isolated double clevis tie, etc., is suitable for welding stud fixing. Fixing ties and clamp-type snap assemblies are suitable for fixing pipes, hoses, wire harnesses, etc.
Plate edge clips are suitable for fixing metal or sheet edges of thickness not exceeding 3mm. Heavy-duty retainers are suitable for wire diameter ' 35mm2. Cable conduit supports are suitable for lifting the cable from the frame rail to separate the cable from the protruding body parts to prevent cable wear. Connector snaps are suitable for fixing high-voltage connectors. Bellows snap is suitable for fast-fixing bellows.
Bellows protection: It uses closed-end bellows whose characteristics are wear-resistant, flame retardant, heat-resistant, etc. The temperature resistance of bellows ranges from -40 to 150' and can also reach 200' for a short time. The common materials on the market are PA (nylon), PE (polyethylene), and PP (polypropylene), respectively. Each has its advantages in terms of flame retardancy, wear resistance, and resistance to bending fatigue. The bellow's color must be orange to distinguish the entire vehicle's low-voltage wiring harness. And use rubber sheath plastic sealing, PVC tape wrapping, and cable fixed seal.
Tube protection: For the wire harnesses arranged in small spaces or special parts, special wire harnesses need to be used to shield and protect. The general pipe guard has stable chemical properties, non-aging, strong corrosion resistance, and other characteristics.
Guard protection: For the high-voltage harnesses arranged in the chassis part (battery total positive and negative) protection method, the design of the guard plate to consider waterproof, anti-sand splash, anti-cuts, and other factors. Most shields use ABS + PC with high impact, high heat resistance, low temperature with high impact strength, and flame resistance.
Sheath protection: parts can be used for easy damage and impact since the rolled sheath. Its characteristics are high-temperature resistance, impact resistance, cut resistance, lightweight and easy installation.
Tape Protection: The tape is used for various applications for wire harnesses. It is often used for protection, bundling, insulation, flame retardant, marking, and other functions. High-voltage wire harnesses are made of flame-retardant PVC tape, which can withstand temperatures up to 80'.
Choosing a Conductor for Your Cable ' A practical guide
By Multi/Cable
INTRODUCTION:
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At the core of your standard or custom cable is a conductor, the metallic wire which allows for the flow of electric current. The success of your application depends on the conductor's ability to effectively carry the electrical load ' without breaking, corroding, oxidizing, or otherwise failing ' throughout the product's lifetime.
Thus, as a key component of your cable and your overall application, the conductor should be selected carefully, with thought given to its size, material, flexibility, conductivity, and service temperature, among other factors.
This guide will walk you through the preliminary considerations that should be made before ordering your cable, including your application requirements, environmental conditions, and electrical parameters.
Conductivity & Cost
Metals are the best conductors of electric charges'but not all metals are equally up to the task. Table 1.1 shows the top electric conductors (the list includes both pure metals and alloys).
Corrosion
If the cable will be used in an environment with high humidity or near salt water, or with certain connectors which require the conductor to be exposed, bare copper could quickly corrode. In these situations, utilizing a copper alloy or tinned copper would offer additional protection from corrosion.
Service Temperature
If the application requires high temperatures, a copper conductor with silver plating or nickel plating would be recommended. As shown in Table 1.2, plating can drastically increase the service temperature and prevent oxidation of copper conductors. While nickel is less conductive of electricity than copper, it is the best choice of coating for applications requiring very high and sustained temperatures.
Typical Conductor Materials
Table 1.3 examines some of the more typical conductor materials with their pros and cons.
There are two options for the construction of your cable's conductors: stranded and solid. Stranded means multiple smaller conductors are twisted together to make a larger conductor. A solid conductor refers to a single, solid wire. Each construction has benefits and drawbacks'so again, the conditions of your application should be considered when making this selection.
Stranded Conductors
Stranded conductors consist of multiple thinner conductor wires combined to act as a larger conductor with a higher gauge. Multiple conductor stranding options are available, depending on your needs (see Table 2.1).
The primary benefit of stranding is flexibility'the construction of stranded conductors makes them less rigid and stiff than their solid counterparts. As a rule, higher conductor flexibility can be achieved by increasing the number of strands, and decreasing the strands' diameter.
While stranded conductors are typically more expensive than solid conductors, they also offer easier installation and longer lifespan (in typical applications), so in the long term they may be a more cost-effective choice.
Stranded Conductor Applications ' Flexible stranded conductors are a good choice for applications such as circuit boards, where a wire may need to twist and bend intricately. Stranded is also a good choice where the conductor will be subject to repetitive motion or to vibration (such as in robotics), as they can endure these factors better than a solid conductor.
Solid Conductors
As the name suggests, a solid conductor consists of a single metallic core. This is usually much thicker than the individual wires found in stranded conductors.
While this option is less widely used, and offers less flexibility, solid conductors are more rugged and durable than their stranded counterparts. And thanks to their simple construction, solid conductors also offer the benefit of lower cost.
Because a solid conductor lacks the spaces between multiple wires, its diameter can be more compact than a stranded conductor, without a decrease in carrying load. This lack of empty spaces also makes solid conductors better at preventing electronic interference.
However, it is important to remember this rigidity can also be an obstacle in many applications. If used in an environment where the cable is subject to frequent motion, a solid conductor will become worn more quickly. Thus, a cable that was initially lower cost will turn out to be less cost-effective. This factor may be disregarded in applications intended to have a shorter lifespan.
Solid Conductor Applications ' Because of their inherent durability, solid conductors are frequently used in applications where harsh conditions may be present'especially if the conductor will be exposed to adverse weather. When corrosion is possible, a solid construction can offer better performance and a longer lifespan. Both blasting wire (which connects a detonator to an explosive device) and direct burial wire (e.g., used to connect homes to a power transformer) utilize solid conductors.
Once you have determined the exact conductor type needed for your application, your next question will be, how many conductors do I need?
Depending on the requirements of your application, your cable can have one or more conductors ' even hundreds of them. The typical range is 2'100, but the number will ultimately be determined by the needs of your application ' how many circuits it contains that need to be connected, and whether spare wires are desirable.
The size of the conductor wires should be selected based on the necessary power load of your application, as well as any physical requirements your application has.
Refer to the Stranded Conductor Data (Table 5.1) and Solid Conductor Data (Table 5.2) tables for information on sizing and power to find the AWG size that meets your needs.
About AWG ' In the United States, wire sizes are measured with the American Wire Gauge (AWG). AWG is a standardized stepped wire gauging system for the diameters of round, solid, nonferrous, electrically conductive wire. Higher numbers indicate cables with smaller diameters.
Current-Carrying Capacity
Can your conductor(s) safely carry the necessary current? Of course, higher voltages mean higher temperatures, but there's more to consider. Don't overlook these factors, which can contribute to overheating:
Voltage Loss
Voltage loss does not typically need to be considered unless your wire run will be quite long (25' or more). In these situations, voltage loss can be minimized by appropriately selecting your conductor:
ABOUT MULTI/CABLE
Multi/Cable Corporation is a leading manufacturer of multi conductor, multi-pair / triad and specialty composite wire and cable. Since , we have supplied customers around the world with cables for their most critical applications. Should you require more data for your application, visit www.multicable.com, or contact their experts at (860) 589-
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