High voltage cable assemblies for electric vehicles

High voltage cable assemblies for electric vehicles

• 2025-03-03 09:08:33
• by Admin

III. Status of standardization of electric vehicle cables

In response to the above challenges and requirements for high-voltage cables for electric vehicle applications, it is necessary to establish new cable standards to meet the needs of suppliers, harness manufacturers, and OEMs.

The Working Group on Vehicle Cables of the Electrical and Electronic Sub-Technical Committee of the International Organization for Standardization Technical Committee for Road Vehicles (ISO/TC 22/SC 3/WG4) is doing this work.

As seen in ISO 6722, the standard based on common 60V cables has been revised to meet the needs of 600V cables. However, as most of its requirements are still very general and often do not take into account the special design required for high-voltage cables, a similar revision has been made to ISO 14572.

The standardization of high-voltage cables for voltages higher than 600 V was the subject of a working group on automotive wiring, ISO 17195. The standard number was ISO 17195, which was later merged into the new standards program ISO 19642 as part of the ISO 19642-X series of standards.

SAE adapted the current high-voltage (rated 600 V) specification SAEJ1654 to the requirements of high-voltage cables and to cover rated voltages from 600 to 1,000 V. The newly created and published standard SAE J2840 defines cables as shielded types.

LV is the common procurement specification of the five major German automotive companies and has introduced the standard LV 216 for high-voltage cables for electric vehicles with a rated voltage of 600 V. It covers both single-core and multi-core shielded cables.

China's national automotive industry standard for high-voltage shielded cables has been released and implemented, and its rated voltage will reach DC1500V/AC1000 V. The standard number is QC/T1037-2016.

IV. High-voltage cable structure design for electric vehicles

Standard products and grudlucirv requirements are difficult to define. The purpose of this paper is to address basic design ideas to overcome the challenges described above by applying advanced high voltage cable structure principles.

1 Conductor design

The flexibility of high voltage cables is mostly determined by the design of the conductor. This is why high voltage cables use special conductors with a large number of very small diameter monofilaments. A certain number of monofilaments are first stranded and then re-stranded concentrically to form the flexible conductor required for high voltage cables.

Another advantage of the large number of strands is better resistance to bending. The shorter pitch of the strands also improves the bending life of high-voltage cables.

2 Insulation materials

Insulation materials are selected primarily for heat resistance requirements and mechanical strength. Compared to standard battery cables, it is reasonable to choose softer materials so that the specially designed stranded conductors remain flexible.

3 Cable Formation

Cables with multi-cores usually need to strand the wire core. To compensate for the deformation caused by stranding the cores of high-voltage cables, special equipment for so-called de-twisting is required. In this process, special stranding machines are equipped with a pay-off reel that rotates in the opposite direction to the stranding direction. This is necessary to prevent deformation of the cable tension.

Depending on the construction of the cable, filling is usually used to ensure a high degree of concentricity of the shielded cable and ultimately to obtain a satisfactory high-voltage cable. The use of wrapping tape in the stranded cable core maintains the flexibility of the cable.

4 Shielding

Due to EMC (Electro Magnetic Compatibility) requirements, a braided shield is formed using multiple copper wires. Tinned copper wire makes it more resistant to environmental influences such as oxidation. The use of thin copper wires maintains the flexibility of the design, and the shielding needs to have a coverage of over 90% to overcome the EMI problems described earlier.

For different needs of shielding effectiveness, braided shielding can be combined with various other types of shielding such as Aluminum Composite Conformal Film. Shields

A non-woven fabric can be wrapped around the shield to ensure that the sheath can be easily peeled off during assembly.

5 Sheathing

As with the insulation of the core, the sheath material is selected according to the thermal and mechanical requirements. Environmental properties such as resistance to liquids and abrasion are also particularly important for the sheath due to direct contact. These properties depend primarily on the type of sheath material selected and, to some extent, on the design of the sheath construction.

If special requirements, such as overcoming abrasion from the environment of the vehicle in which it is installed, require increased abrasion resistance, this needs to be taken into account when selecting the material. Ten test equipment are used to simulate real-world conditions to verify these properties.

The choice of softer materials benefits from flexibility, which may lead to lower abrasion resistance in high voltage cables. The extruded jacket should be a bright orange color according to the relevant specifications, and special markings warning of high voltage can also be added according to the regulations. 

V. Characteristics and optimization of high voltage cables for electric vehicles

A perfectly complex design and the use of high-quality materials will lead to expensive cable costs. Experience has shown that specific high-voltage cables can often be tailored by optimizing the cross-section, temperature requirements, flexibility, and shielding effect. Weight and cost savings can be realized, and oversizing and excessive components can be avoided.

1. Optimization of cross section and temperature rating

The selection of cables is mostly based on ambient temperature and transmission current specifications. In this respect, the most important characteristics are the “cable cross-section” and the “thermal class of the material used in the cable”.

The voltage drop in the conductor is transformed into heat by heating the conductor of the high-voltage cable. This heat can be partially transferred to the environment, resulting in a lower conductor operating temperature. Lower temperature gradients can transfer less heat. Cables with continuous load currents can

withstand the highest rated temperatures. This temperature can cause deterioration of the materials used.

The challenge for cable designers is to design the most appropriate cable for the application: Over sizing of conductors can lead to increased cost and weight with larger outside diameters. In the worst case, considering only the highest possible load current and ambient temperature will lead to the use of large cross-section cables with high-temperature resistant materials such as organofluorine or silicone materials.

Determining the relationship between current and load ambient temperature makes sense from a technical and economic point of view. The periodic dynamic current peaks of a real drive should be taken into account, allowing a reasonable definition of the worst-case load current and peak current.

A prerequisite for a good design is the knowledge of the basic conditions, e.g., the ambient temperature and the cable load must be determined first. Generally, large cross-section high-voltage cables have a large inertia in terms of temperature variations so that current peaks during the acceleration or deceleration of a vehicle do not lead to a large influence on the conductor temperature. Short-term temperature peaks are sometimes permitted even if they are exceeded in the above-defined cable temperature classes.

The ability of a high voltage cable to handle these peaks is usually defined by the thermal overload performance of the defined temperature class of the cable. Thus, cables do not need to be designed for higher operating temperature ratings, and it is not necessary to use cables that exceed the specified operating temperature. The resident load current, as well as the single pulse or series of pulses, can be considered together with various parameters such as ambient temperature.

A combination of theoretical foundations and experience gained in practice makes it possible to identify, see, and obtain high-voltage cables optimized for the application.