In the electric vehicle, the high-voltage wiring harness is regarded as the “energy artery”, and its arrangement gap and fixing standard are directly related to the safety, electromagnetic compatibility (EMC) and reliability of the vehicle. The requirements of the relevant standards are detailed below from a number of perspectives.
The arrangement clearance shall be appropriate, and the operability of assembly and repair shall be fully considered.
Generally, a space of not less than 200mm shall be reserved at all connector positions to facilitate connection and disconnection operations. The connection between the connector and the component shall be mechanically stress relieved.
Considering that the current of different models is the same, the distance between high and low voltage parallel lines of commercial vehicles must be greater than 400 mm, and the distance between high and low voltage parallel lines of passenger cars must be greater than 200 mm. If the actual situation does not meet this distance, it can be considered to run perpendicular to each other.
Layout clearance requirements
Safety clearance between high-voltage harness and peripheral components
Clearance with vehicle body and non-high-voltage parts:
- The minimum dimension between the high-voltage harness and the outline of the vehicle shall be kept above 110mm to ensure that there is a sufficient safe distance between any non-external high-voltage component and the vehicle body.
- The clearance between adjacent parts shall be ≥ 15mm and the dynamic clearance shall be ≤ 25mm.
- The clearance between the high-voltage harness and the stationary parts shall be ≥ 10 mm.
Clearance to moving parts:
- The high-voltage harness shall not interfere with the moving parts, and the distance between them shall not be less than 50mm.
- Clearance with moving parts (such as drive shaft, suspension, etc.) shall be ≥ 25 mm
Clearance from heat source:
- The high voltage harness shall be kept away from the heat source (such as engine exhaust pipe and other high heat parts), and the distance shall be at least 200mm.
- If the distance requirement cannot be met due to objective reasons, the harness shall be wrapped or covered with flame retardant heat insulation cotton or a cover that reflects heat energy.
- The ambient temperature shall be lower than 125 ℃.
Spacing between high and low voltage harnesses
Parallel trace distance:
- Passenger car:the distance between high and low voltage parallel wiring must be greater than 200mm
- Commercial vehicle:the distance between high and low voltage parallel wiring must be greater than 400 mm
- If the actual situation does not meet this distance, it can be considered to run perpendicular to each other.
EMC-related spacing:
- It is recommended that the distance between the connecting harness of the interference source and the connecting harness of the components susceptible to interference shall not be less than 10 cm.
- It is recommended that the distance between the high-voltage harness and the metal structure of the vehicle body should not exceed 10 cm. In principle, the closer the better.
- In case of layered arrangement, the layered distance between high and low voltage harnesses shall be 200 ~ 300 mm.
Connector operating space
- A space of not less than 200mm shall be reserved at all connector positions to facilitate connection and disconnection operations.
- Connections between connectors and components shall be mechanically stress relieved
- An appropriate length shall be reserved for the plugging or connecting part, and the recommended value is 150mm
Bending radius requirements
- The bending radius of the harness shall be ≥ 6d (D is the diameter of the high-voltage harness)
- When wire diameter D ≤ 15mm, bending radius ≥ 3D; When wire diameter D > 15 mm, bending radius ≥ 5D
- In general, the minimum bending radius is equal to 5 times the outer diameter of the cable.
Fixed standard requirements
For the layout of the high-voltage harness, the harness shall be protected as much as possible to minimize the relative movement between the harness and the vehicle body.
Due to the high strength of the high-voltage wiring harness, different treatments are required according to the length of the wiring harness. Generally, it is required to use smooth and burr-free brackets, trunking, clamps, ties, etc. For fixing.
When fixing with cable ties, the fixing method shall be fully considered to facilitate the selection of appropriate cable ties for fixing and avoid the risk of fixing failure.
Fixation point spacing requirements
The distance between the harness fixing protectors must not be greater than 400 mm. The high-voltage wiring harness shall not interfere with the moving parts, and the distance between them shall not be less than 50mm.
The power battery of the electric vehicle is arranged in the lower bottom plate at the rear of the vehicle. The high-voltage wiring harness led out from the front end of the battery passes under the bottom plate of the vehicle and is close to the ground. It is necessary to add corrugated pipe protection outside the cable to prevent the high-voltage wiring harness from being hit by stones splashed on the road during driving.
Due to the demand of space in some positions, the harness cannot be protected by corrugated pipe. The scheme of adding plastic trunking outside the high-voltage harness can be considered to protect the harness.
Classified by the cross-sectional area of the harness:
- The sectional area of high-voltage harness shall be more than 16 mm ², and the clearance between two fixed points shall be ≤ 300 mm.
- The sectional area of the high-voltage harness is less than 16 mm ², and the clearance between two fixed points is ≤ 200 mm.
General requirements:
- The distance between the wire harness fixing protectors must not be greater than 400 mm
- It is generally required to set a fixing buckle every 200 ~ 300 mm.
- When laying along a straight line, the distance between adjacent fixing points shall be 150 ~ 250 mm.
The outlet end of the connector is fixed
- The first fixing shall be carried out at the position where the outgoing line at the tail of the connector is not more than 120mm.
- Distance from the outlet of HV connector to the first fixing point ≤ 100 mm
- The high-voltage harness near the tail of the connector shall not be bent or rotated, and it shall be fixed when the length of the high-voltage harness is ≤ 120 mm.
Fix at the bend
- Fixing points shall be provided at the front and rear ends of the bend of the high-voltage harness.
- It must be fixed within 50mm on both sides of the bending point to bear the bending force.
- Fix at both ends of the bend, and the distance between the fixing point and the connector shall be ≤ 150mm.
Fixture Selection and Requirements
Type of fixings:
- Fastening shall be done with smooth and burr-free brackets, trunking, clamps, ties, etc.
- The fixings shall be insulated and protected against corrosion and rust
Protective measures:
- The wiring harness in the chassis area shall be wrapped with metal braided network pipe or corrugated pipe to enhance the impact resistance.
- Rubber sheath or bellows shall be installed when passing through sheet metal holes and sharp edges.
- Connectors in splash zones shall be bagged
Inspection requirements after installation
- Insulation resistance test:measured with a megohmmeter, ≥ 500 MΩ at 1000V DC
- Withstand voltage test:apply 1500V DC voltage for 1 minute, no breakdown or flashover
- Temperature rise test:with rated current, the monitoring temperature shall not exceed 125 ℃.
The layout clearance and fixing standard of high-voltage wiring harness are the core elements of the safety design of new energy vehicles. In terms of clearance, it is necessary to focus on the safe distance from the car body, moving parts, heat source and low-voltage wiring harness. In terms of fixation, it is necessary to ensure that the spacing between fixed points is reasonable, the connector outlet is reliably fixed, the bending is strengthened and fixed, and appropriate protective materials are selected. These standards jointly guarantee the safe and reliable operation of high-voltage wiring harness under complex working conditions such as vibration, collision and thermal load.
