On the Characteristics and Safety Design Requirements of High Voltage Wire Harnesses

The operational characteristics of pure electric vehicles determine the particularity of high-voltage wiring harnesses; Compared to low-voltage harnesses, high-voltage harnesses have the following characteristi:

1. High voltage. The rated voltage of vehicle power batteries is usually above 300V, and some vehicles may even reach 600V or above, requiring the insulation material of the wiring harness components to have higher voltage resistance.

2. Sealing performance. If the bus output connector is located at a lower position and needs to face the erosion of water and dust, it requires a higher level of protection. The protection level of connectors generally requires IP67, and some special parts require IP6K9K.

3. High heat resistance. When the vehicle operates with high current, the Joule effect generates heat, causing the temperature of the wiring harness itself and its surroundings to rise, requiring the wiring harness to have better heat resistance performance. The heat resistance performance of high-voltage wire harnesses usually needs to reach 125 ℃ or even higher.

4. Anti electromagnetic interference. During the operation of electric vehicles, the constantly changing electrical loads and the extensive use of variable frequency technology in the system cause severe fluctuations in the voltage, current, and frequency of the wiring harness, resulting in significant electromagnetic interference. Usually, high-voltage connectors are shielded at 360 °, and shielded cables are used for high-voltage cables.

5. Durability performance. The high-voltage wiring harness should have properties such as temperature resistance, weather resistance, corrosion resistance, vibration resistance, and cable abrasion resistance, and have a large safety margin and connection life to ensure the long-term reliable operation of the vehicle.

Connector: The function of a wire harness connector is to ensure that cables and electrical equipment can be conveniently and reliably connected and disassembled.

The selection of high-voltage connectors for pure electric vehicles usually has the following requirements:

1) Electrical performance. In order to cope with high voltage and high current usage environments, connector terminals are usually designed with special structures to increase contact area and reduce contact impedance; Cooperate with the application of shielded cables,

The connectors are mostly made of metal materials or designed with shielding structures inside to achieve a 360 ° shielding structure design; According to high-voltage safety standards, the voltage resistance of the connector should be>2U+1000V (AC), and the insulation resistance should be ≥ 20M Ω

2) Environmental performance. The working temperature of connectors is usually required to be -40~125 ℃; Corrosion resistant, oil resistant, and plastic materials with flame retardant properties; Minimum connector protection

The protection level is IP67, and some special requirements require reaching IP6K9K.

3) Mechanical performance. The connector is resistant to vibration and impact; Equipped with self-locking and foolproof structures; Plug and unplug life>500 times; Equipped with a loop interlocking structure design.

Safety requirements: High voltage warning signs, B and voltage wire marking requirements

Standard: The outer skin of cables and harnesses is orange, and high-voltage connectors can be distinguished by the harnesses connected to them

Standard: Yellow background, black frame, black arrow

Safety design requirements for high-voltage connectors:

High voltage connectors should not be able to open without the use of tools, except for the following three situations:

a) After the high-voltage connector is separated, it should meet the protection level requirements of IPXXB

b) High voltage connectors require at least two different actions to separate them from each other's docking ends, and there is a mechanical locking relationship between the high voltage connector and some other mechanism. Before the high voltage connector is opened, the locking mechanism must be opened using tools,

c) After the high-voltage connector is separated, the voltage of the live part in the connector can be reduced to no more than 30 Va. c. (rms) and no more than 60 Vd. c. within 1 second

High voltage PDU safety design requirements:

a) The interior of the passenger compartment and cargo compartment should meet the IPXXD protection level requirements, while the exterior of the passenger compartment and cargo compartment should meet the IPXXB protection level requirements;

b) High voltage warning sign, designed for dismantling or uncovering protection in industrial and commercial areas, must meet the following requirements within 1 second of opening the casing: -- The circuit voltage should drop to no more than 60

Vd.c.

c) The connection impedance between the PDU housing and the level table should not exceed 0.12

Charging socket requirements: IP55 when plugged in and IP54 when covered with a protective cover

Requirements for AC charging sockets: When disconnected, the insulation resistance should be greater than 1M Ω, and there should be terminals connected to the electrical platform.