Wiring harnesses serve as the “nervous system” of equipment and vehicles, responsible for power distribution and signal transmission. This analysis covers wiring harness classification, core materials, lifespan evaluation, and key selection criteria to empower engineers and users with precise decision-making.
1.1 Application-Based Classification
- Automotive Wiring Harnesses: Include engine harnesses, instrument panel harnesses, etc., with structures like H-type, T-type, and E-type to suit different layout requirements.
- Industrial Control Harnesses: Used in new energy equipment, security systems, etc., emphasizing stable electrical signal control.
- Power Control Harnesses: Such as switch power supply cables, specialized for efficient power transmission.
- Data Transmission Harnesses: Including HDMI, USB, etc., ensuring high-speed signal upload and download.
1.2 Function-Oriented Classification
- Display Driver Harnesses: Specifically designed for display screen driving.
- Shielded Harnesses: Utilize metal shielding layers to eliminate electromagnetic interference, suitable for precision systems like airbag sensors.
1.3 Voltage Level Classification
- High-Voltage Harnesses (≥300V): Core components for new energy vehicles, transmitting drive power.
- Low-Voltage Harnesses (≤60V): Primarily for vehicle-wide signal transmission, commonly at 12V.
1.4 Standard Certification Classification
- National Standard Harnesses: Comply with Chinese national standards.
- German Standard Harnesses: Adhere to DIN 72550, known for thin insulation and high flexibility.
Combining the above categories can derive specialized products like wind power connection harnesses and custom communication equipment harnesses.
2. Detailed Analysis of Wiring Harness Materials
2.1 Metallic Conductors
- Copper and Alloys: Pure copper offers optimal conductivity; brass provides high mechanical strength; terminals are often tin/silver/gold plated for oxidation resistance.
- Aluminum and Alloys: Preferred for lightweight applications but require larger cross-sectional areas to compensate for lower conductivity.
- Specialty Metals: Gold and nickel for high-temperature scenarios; iron and steel as reinforcement materials.
2.2 Insulation and Sheathing
- PVC: Low cost, resistant to 70-90°C, suitable for standard environments.
- XLPE (Cross-linked Polyethylene): Heat resistant from 90-105°C, short-term tolerance up to 130°C, suitable for instruments and controllers.
- Silicone Rubber/Fluoropolymers: Withstand temperatures above 150°C, ideal for engine bays.
- Nylon/PBT: Abrasion-resistant and flame-retardant, widely used for sheathing and connector housings.
2.3 Protection and Sealing Materials
- Conduits (Corrugated Tubes): Made from PA or PVC, providing water and abrasion resistance.
- Sealing Tapes: PVC tape, cloth tape for harness wrapping.
- Rubber Seals: EPDM and silicone rubber for long-lasting sealing.
2.4 Special Function Materials
- Shielded Cables: Aluminum foil or braiding to combat electromagnetic interference.
- Coaxial Cables: Specifically for high-frequency signals like GPS, cameras.
Application Example: New energy vehicle high-voltage harnesses often use “aluminum conductor + silicone rubber insulation,” balancing lightweight and high-temperature resistance.
3. Wiring Harness Service Life
3.1 Methods for Identifying Aging
- Visual Inspection: Cracking, hardening, or discoloration of insulation; conductor oxidation (blackened copper, white spots on aluminum).
- Functional Testing:
- Resistance Check: Abnormal increase suggests internal break.
- Insulation Resistance: Requires immediate replacement if below 0.5 MΩ.
- Abnormal Phenomena: Starting difficulties, sudden increase in fuel consumption, overheating wires, or sparks.
3.2 Factors Influencing Lifespan
- Usage Environment: High temperature, humidity, and chemical corrosion accelerate aging.
- Material Quality: Pure copper conductors and high-temperature resistant insulation significantly extend life.
- Load Conditions: Overload operation drastically shortens service life.
3.3 Core Measures to Extend Lifespan
- Material Selection: High-purity oxygen-free copper, XLPE, or PUR sheathing.
- Enhanced Protection: Conduits and wire protection channels to reduce mechanical wear.
- Regular Maintenance: Check insulation resistance quarterly; spray protective agent on engine bay harnesses annually.
- Proper Installation: Avoid overloads; optimize routing to minimize vibration.
Lifespan Reference:
- Automotive Harnesses: Design life ~10 years, requires key inspection at 3-5 years.
- Industrial Harnesses: Quality products can last the equipment’s life; inferior products may last only 1-5 years.
4.1 Conductor Selection Principles
- Copper Wires: Preferred for new energy high-voltage harnesses (oxygen-free copper); low-voltage harnesses can use stranded copper wires.
- Aluminum Wires: Suitable for lightweight applications but require processes like laser welding to ensure connection reliability.
4.2 Insulation and Sheathing Selection Matrix
| Environmental Condition | Recommended Material | Temp Range | Core Advantage |
|---|
| Normal Ambient | PVC | 70-90°C | Low cost, acid/alkali resistant |
| Medium-High Temp Areas | XLPE | 90-105°C | Optimized heat resistance, cost-effective |
| Extreme Temp (Engine) | Silicone/Fluoropolymer | Above 150°C | Anti-aging, good mechanical flexibility |
| High-Flex/Drag | PUR Sheath | -40°C~125°C | Abrasion resistance 5x PVC |
4.3 Compliance Requirements (e.g., ISO 6722-1)
- Conductor: High-purity oxygen-free copper, compliant cross-sectional area.
- Insulation Materials: Pass flame retardancy tests (flame extinction time ≤70s).
- Environmental Testing: Withstand high/low temperature cycling (-40°C to 150°C) and salt spray corrosion.
- Shielding Effectiveness: Coverage ≥85%, meeting electromagnetic compatibility.
4.4 Special Considerations for New Energy Vehicles
- High-Voltage Harnesses: Resist 600V/900V voltage, increased wall thickness, and materials must pass 150°C endurance tests.
- Lightweight Design: Aluminum conductor + thin-wall XLPE can reduce weight by 40%, but requires rigorous validation of connection reliability.
5. Wiring Harness Maintenance and Replacement Decision Tree
- Slight Aging (local cracks, slight oxidation):
- Clean connections, apply conductive paste.
- Wrap with high-temperature resistant insulating tape (e.g., 3M 2228 series).
- Moderate Aging (hardened insulation, abnormal resistance):
- Replace the local harness section, and add protective conduit.
- Severe Aging (broken insulation, exposed conductor):
- Immediate full replacement, prefer OEM or improved harness types.