Electric vehicle high voltage cable structure design

- Oct 05, 2019-

Standard products and very specific requirements are difficult to define. The purpose of this paper is to solve the basic design ideas and overcome the challenges described above by applying advanced high voltage cable construction 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 bundled and then concentrically twisted to form the soft conductors required for the high voltage cable.

Another benefit of having more roots is better resistance to bending. The twisted pitch is shortened, which also improves the bending life of the high voltage cable.

2. Insulation Materials

The choice of insulating material is mainly considering heat resistance requirements and mechanical strength. Compared to standard battery cables, a softer material can be chosen to keep the specially designed stranded conductor flexible.

3. Cable

When the cable is multi-core, it is usually necessary to twist the core. In order to compensate for the deformation caused by the twisted high-voltage cable core, it is necessary to use a special device called back-twist. In this process, the dedicated stranding machine is equipped with a pay-distributing disc that rotates in the opposite direction with respect to the twisting direction. This is necessary to prevent the deformation tension of the cable.

Depending on the structure of the cable, padding is usually used to ensure a high degree of concentricity of the shielded cable, resulting in a satisfactory high voltage cable. The use of a strap in the twisted cable core maintains the flexibility of the cable.

4. shield

Due to EMC (electromagnetic compatibility) requirements, multiple copper wires are used to form a braided shield. Tinned copper wire can make it more resistant to environmental influences such as oxidation. The flexibility of the design can be maintained with fine copper wire.

Shielding requires a coverage of over 90% to overcome the EMI problem described earlier.

The shielding effect can be combined with other shieldings, such as aluminum-plastic film. A layer of non-woven fabric can be wrapped around the shield to ensure easy peeling of the jacket during assembly.

5. jacket

As with the insulation of the core, the jacket material is selected according to thermal and mechanical requirements. Due to direct contact, environmental properties such as resistance to liquids and abrasion are also of particular importance to the sheath. These characteristics are mainly determined by the type of jacket material selected and, to some extent, by the jacket structure design.

If special requirements, such as overcoming the wear and tear of the installed vehicle environment, require increased wear resistance, this needs to be considered when selecting materials. Test equipment is often used to simulate real-world conditions to verify these characteristics.

Choosing a softer material benefits from flexibility, which can result in lower wear resistance of the high voltage cable.

According to the relevant regulations, the extruded jacket should be a bright orange, and special warning high pressure markings can be added according to regulations.