Wire harnesses serve as the circulatory system of modern vehicles, electronics, and industrial systems. Selecting the appropriate type of wire is critical to ensure safety, durability, and efficient performance. The following outlines the key standards for wire selection, based on application scenarios, electrical requirements, and color coding practices.
1. Selecting Wire Types Based on Application Scenarios
Automotive Industry:
Wiring in vehicles must withstand harsh environments.
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Engine Compartment: Due to high temperatures, vibrations, and exposure to oil, wires such as FLRY-A (German standard) are preferred for their heat, oil, and vibration resistance.
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Door Wiring: Frequent opening and closing require flexible wires. AVSS wires with thin-wall insulation offer excellent flexibility.
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Sensor Wiring: For weak signal transmission (e.g., knock or crankshaft position sensors), electromagnetic shielding wires are essential to prevent signal interference.
Consumer Electronics:
Compact, high-performance devices such as smartphones and tablets demand miniaturized, highly flexible wires.
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FFC (Flexible Flat Cable): Commonly used to connect displays, cameras, and motherboards. It allows customizable conductor count and pitch, optimizing space and performance.
Industrial Equipment:
Automated production lines involve heavy vibration and strong electromagnetic interference (EMI).
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Industrial Wiring: Requires high durability and interference resistance. Double-shielded wires and wires with abrasion- and corrosion-resistant materials are typically used in environments with machinery like CNCs and industrial robots.
Aerospace Industry:
Wire selection must meet extreme performance standards.
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Aerospace Wires: Lightweight, high-strength, heat- and radiation-resistant materials are essential. Silver-plated copper wires are commonly used for excellent conductivity and reduced weight. Insulation materials like polyimide provide reliability in space and high-altitude environments.
2. Determining Wire Cross-sectional Area by Current and Power
Wire cross-sectional area determines current-carrying capacity.
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Basic Principle: The higher the electrical power, the larger the required wire size.
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Continuous Load: Use 60% of the wire’s rated current to ensure safety.
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Intermittent Load: Wires can carry 60%–100% of the rated current depending on usage duration.
Examples:
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Automotive high-beam lights often use 1–2.5 mm² wires due to higher power demand.
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Small lights like dashboard indicators can use wires around 0.5 mm².
Environmental Considerations:
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High Temperature: Poor heat dissipation requires larger wire size.
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Complex Routing & Connectors: Voltage drops increase with longer paths and more connectors, requiring adjustments to wire size.
Useful Formulas:
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I = P / U (Current = Power / Voltage)
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A = IρL / Ud (A = wire area, ρ = resistivity, L = length, Ud = max voltage drop)
3. Considering Wire Color Coding
Color coding is crucial in wire harness design for efficient assembly and maintenance.
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No Universal Standard: Different manufacturers follow their own specifications.
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Common Practice:
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Black: Ground wires
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Red: Power supply
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Blue: Signal circuits
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Green: Control circuits
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Using single, dual, or even triple color combinations allows clear identification of circuit functions, reducing error risk and improving troubleshooting efficiency.
Conclusion
Wire selection in the wire harness industry is a multi-faceted process involving environmental adaptation, electrical performance, and human usability. By aligning wire type, size, and color with specific application needs, engineers ensure safe, durable, and efficient systems—whether on the road, in the factory, or out in space.