Automotive EV High Voltage Line: Principle and Characteristic Analysis

# Automotive EV high-voltage line: principle and characteristic analysis

## Introduction

With the vigorous development of the new energy vehicle industry, electric vehicles (Electric Vehicle, EV) have become an important development direction of the automotive industry. In electric vehicles, as the core component of the power transmission system, the high-voltage wiring harness carries the important task of power transmission and control signal transmission. The purpose of this paper is to deeply analyze the principle and characteristics of EV high voltage line and discuss its key role in electric vehicles.

## The basic principle of high-voltage wiring harness

### Definitions and Functions

Automobile EV high-voltage wiring harness refers to a wiring harness composed of high-voltage wires connecting the battery and the motor. Its working voltage is usually above 400V, which is much higher than the 12V working voltage of traditional automobiles. The high-voltage wiring harness is not only responsible for the transmission of electric energy, but also undertakes the task of controlling signal transmission. It is the "nerve" and "blood vessel" of the electric vehicle power transmission system ".

### Components

The high-voltage wire harness is mainly composed of high-voltage connectors, high-voltage cables, grounding terminals, cable ties, outsourcing materials, adhesive tapes, heat shrinkable sleeves, rubber sleeves, mounting brackets and other auxiliary materials. Among them, the high-voltage cable is the core part, which is divided into shielded wire and non-shielded wire, and the wire diameter ranges from 2.5mm ² to 120mm ². The shielded wire also has a shielding layer and a double-layer insulation structure to improve electromagnetic compatibility and electrical safety.

### Working principle

In electric vehicles, the high-voltage wiring harness distributes the electric energy delivered by the power battery assembly to various electrical equipment, such as motor controllers, air-conditioning compressors, PTC heaters, etc. When the vehicle is running, the current passes from the power battery through the DC bus, the branch box, and the high-voltage line of the motor controller, and finally reaches the drive motor to generate driving force. At the same time, the mechanical energy (such as braking efficiency) generated by the drive motor during driving can also be converted into electrical energy, which is charged back to the power battery through the reverse path.

Characteristic analysis of## high-voltage wire harness

### High voltage characteristics

Since the working voltage of the high-voltage wiring harness of the new energy vehicle is above 400V, it must have good insulation performance and electrical safety performance. The insulation materials of high-voltage cables are usually cross-linked polyethylene and silicone rubber and other high-temperature, wear-resistant, and corrosion-resistant materials to ensure long-term stable operation.

### High temperature and wear resistance

The motor and battery of electric vehicles need to work in a high temperature environment, so the high-voltage wiring harness needs to have good high temperature resistance and thermal conductivity. At the same time, the high-voltage wire harness also needs to withstand external forces such as deflection, tension and friction for a long time, which requires that its material and structure design must have good wear resistance.

### Electromagnetic Compatibility and Safety

High-voltage wire harness in the transmission of electrical energy at the same time, but also need to consider the electromagnetic compatibility issues. In order to avoid electromagnetic interference, high-voltage cables usually use shielding design, combined with other shielding measures, such as braided shielding and aluminum-plastic composite film, to ensure the accuracy and stability of signal transmission. In addition, the high-voltage wiring harness is also provided with multiple fuses and protection devices to prevent overcurrent, short circuit and other faults from causing damage to the system.

## Design and wiring of high-voltage wire harness

### Design Points

The design of high-voltage wiring harness needs to consider a number of factors, including electrical performance, mechanical performance, environmental adaptability and so on. In the material selection, it is necessary to ensure that the insulation material, shielding material and sheath material of the high-voltage cable meet the relevant standards and requirements. In the structural design, it is necessary to consider the softness, bending radius, shielding effect, etc. of the high-voltage cable to ensure that it can smoothly pass through the complex wiring path of the vehicle.

### Wiring Precautions

During the wiring process, a series of precautions must be followed to ensure the safety and reliability of the high-voltage wiring harness. For example, a protective structure should be designed when a high-voltage cable passes through a sharp edge or through a hole. Avoid heat sources or keep a sufficient distance from them when arranging. Avoid large elastic friction between cables and cables; The spacing between fixed points of cables arranged in a straight line should be controlled within a reasonable range. Attention should also be paid to the separation of high and low voltages and the hierarchical design in wiring to avoid electromagnetic interference.

## Case analysis

Take the Tesla Model S as an example. The battery fire occurred while the car was charging, which triggered extensive discussions in the industry on the safety of high-voltage batteries. Through in-depth analysis of the incident, it can be found that the design defect of the thermal management system of the high-voltage battery is one of the important reasons for the accident. Therefore, in the design and application of high-voltage wiring harnesses, thermal management issues must be fully considered, and effective heat dissipation and temperature control measures must be taken to ensure the safe and stable operation of the system.

## Conclusion

As the core component of electric vehicle power transmission system, the principle and characteristics of EV high-voltage wiring harness are very important to the performance and safety of electric vehicles. Through in-depth analysis of the composition, working principle, characteristics and design and wiring points of high-voltage wiring harness, we can better understand its role and importance in electric vehicles. In the future, with the continuous development of the new energy vehicle industry, the technology of high-voltage wiring harnesses will continue to improve and improve, providing a more solid guarantee for the safe and efficient operation of electric vehicles.