Popular Science | What is a charging cable? Part 2

How to choose charging cables

 

How to choose charging cables

 

I. Selection of cables for charging station construction

1. Charging stations are divided into single-phase and three-phase. Regardless of whether it is three-phase or single-phase, it is necessary to convert it to the AC incoming line current.

(1) For single-phase charging stations (AC charging stations), I=P/U

(2) For three-phase charging stations (DC charging stations), I=P/(U*1.732)

After calculating the current, select the cable according to the current size.

2. Cable selection can refer to relevant manuals or regulations such as:

(1) Single-phase charging stations are generally 7KW (AC charging stations).

According to I=P/U=7000/220=32A, 4 square millimeter copper core cables should be used.

Within 100 meters, 3*6 square copper core cables are required;

100 meters to 150 meters, 3*10 square copper core cables are required; ‍‍

More than 150 meters, 3*16 square copper core cables are required;

for more than 200 meters, it is better to consider taking other routes.

(2) Three-phase charging station (DC station)

15KW current 23A cable 4 square millimeters

30KW current 46A cable 10 square millimeters

60KW current 92A cable 25 square millimeters

90KW current 120A cable 35 square millimeters

3. Note:

3*6 square cable means three cores 6 square millimeters, wiring requirements: 1 live 1 neutral 1 ground.

5*6 square cable means five cores 6 square millimeters, wiring requirements: 3 live 1 neutral 1 ground.

6 square millimeters measures the cross-section of the cable.

When using aluminum core, the wire diameter should be 1.5-2 times that of copper core.

The above wires are all open wires, not buried.

4. How big a cable should be used for ground installation? It is recommended to calculate the current of the incoming line again based on the power loss of 0.85. The calculation formula is as follows:

For single-phase charging stations (AC charging stations) I=P/(U*0.85)

For three-phase charging stations (DC charging stations) I=P/(U*1.732*0.85)

Note: After calculating the current in this way, purchase cables according to the current size.

For copper wire cables, generally each mm² of copper wire cross-section can support a current of 5~8A; for aluminum wire cables, each mm² can support a current of 3A. When calculating, we must consider the actual conditions such as line loss and heat dissipation and choose the appropriate cable. Common cable cross-sectional dimensions include: 1mm², 1.5mm², 2.5mm², 4mm², 6mm², 10mm², 16mm², 25mm², 35mm², 50mm², 70mm², 95mm², 120mm², 150mm², 185mm², 240mm², 300mm², 400mm², 500mm², 630mm², 800mm², 1000mm², 1200mm², 1400mm², 1600mm², 2500mm².

In ​​addition, all charging stations should have neutral and ground wires. So single-phase requires three-core cables, and three-phase requires five-core cables.

Ⅱ. Selection of home charging cables

When purchasing charging cables for home charging stations, the following key factors should be considered comprehensively to ensure safety, efficiency and compliance with usage requirements:

1. Charging station type and power:

Home charging stations are usually divided into AC charging stations (AC) and DC charging stations (DC). AC charging stations (such as 7kW single-phase or 11kW, 21kW three-phase) are suitable for home slow charging, while DC charging stations are often used in public fast charging stations. Determining the type and rated power of the charging station is the basis for calculating the required cable specifications.

2. Current calculation:

Calculate the required current based on the charging station power and power supply voltage. For AC charging stations, use the formula I = P / U, where P is the charging station power (unit: watt, W) and U is the power supply voltage (unit: volt, V). For three-phase charging stations, use I = P / (U × √3), where √3 is the square root of three, which represents the relationship between the phase voltage and the line voltage of the three-phase circuit. After calculating the current, you can choose the appropriate cable according to the current value.

3. Cable current carrying capacity

Based on the calculated current value, select a cable that can carry the corresponding current. Check the cable specification table or consult a professional to understand the rated current carrying capacity of different cable models. Generally speaking, the copper core cable used in home charging stations can carry 5-8 amperes per square millimeter of copper wire (3-5 amperes for aluminum core wire). Make sure that the current carrying capacity of the selected cable is greater than the actual current demand to leave a margin and ensure safety.

4. Cable material

Copper core wire is usually the first choice due to its good conductivity and low resistance, especially when wiring over long distances, its heat loss is small and its efficiency is higher. Although aluminum core wire has a lower cost, its conductivity is slightly inferior to copper wire, and it has higher requirements for connectors to prevent oxidation. In most cases, copper core wire is recommended for home charging stations.

5. Cable specifications (wire diameter):

Based on the current calculation results and current carrying requirements, select cables of corresponding specifications. For example, for a 7kW single-phase AC charging station, a 4 square millimeter copper core wire is usually recommended. For higher power or three-phase charging stations, cables of 6 square millimeters, 10 square millimeters or even larger specifications may be required. At the same time, depending on the distance from the meter to the charging station, the wire diameter may need to be increased to reduce voltage drop and heat loss.

6. Cable type:

Common types of charging station cables include RVV, VVR, YJV and YJVR. Among them, YJV (or YJVR) cable is often recommended for charging station installation due to its good electrical performance, heat resistance, mechanical strength and environmental protection characteristics. This type of cable usually has cross-linked polyethylene (XLPE) insulation and polyvinyl chloride (PVC) sheath, suitable for outdoor or underground laying.

7. Cable structure:

For AC charging stations, 3 core wires (live wire, neutral wire, ground wire) are usually required, while three-phase charging stations may require 5 core wires (three-phase live wire, neutral wire, ground wire). Make sure the selected cable contains the correct number of cores and color identification to meet electrical specifications.

8. Cable length:

Choose a cable of appropriate length according to the actual installation distance from the meter to the charging station. Note that a cable that is too long may increase the voltage drop and affect the charging efficiency. Therefore, try to choose a shorter cable while meeting the installation requirements. If the distance is long, it may be necessary to increase the cable specifications appropriately according to the above current calculation and wire diameter selection methods.

9. Cable certification and standards:

Make sure that the selected cable meets the electrical safety standards of the relevant countries or regions, such as China GB/T standards, US UL standards, European EN standards, etc. Check whether the cable has certification marks, such as CCC, UL, CE, etc., to ensure product quality and safety.

Can the charging cable, station, and gun be purchased separately?

 

The charging cable, charging station body, and charging gun can be purchased separately. In fact, there is such a sales model in the market, and users can freely combine and purchase these components according to their own needs and budget. The following are several situations for separate purchases:

1. Charging station and charging gun are purchased together.

Many charging station manufacturers will provide an integrated solution, that is, the charging station and the matching charging gun are sold as a whole product. This method is more worry-free for consumers because the manufacturer has ensured the compatibility and safety between the charging station and the charging gun.

2. Charging station is purchased separately.

Users can choose to purchase only the charging station body without the charging gun. This situation is common when the user already has a suitable charging gun, or plans to purchase a charging gun of a specific brand with special functions (such as remote control, intelligent identification, etc.) separately. When purchasing, you need to confirm that the charging station interface type matches the vehicle charging interface.

3. Purchase the charging gun separately

If the user already has a charging station, but needs to replace or purchase an additional charging gun, you can purchase it separately. For example, the original charging gun is damaged or lost, or you want to equip it with a longer, more durable charging gun with special functions (such as waterproof, low-temperature heating, etc.). Similarly, you need to ensure that the charging gun is compatible with the charging station interface and the vehicle charging interface.

4. Purchase or customize the charging cable separately

As the intermediate link between the electric meter, charging station and vehicle, the charging cable may sometimes need to be purchased or customized separately according to the actual installation environment (such as distance, wiring method, protection requirements, etc.). Users can purchase universal cables that meet the specification requirements, or they can choose and purchase them according to the cable parameters or recommended models provided by the charging station manufacturer. When customizing the cable, you may need to consider factors such as cable length, wire diameter, material, sheath type, connector style, etc.

It should be noted that although these components can be purchased separately, their compatibility and safety must be ensured when they are actually used together. When choosing components purchased separately, it is recommended to follow the following principles:

1. Interface compatibility

Confirm that the charging station interface, charging gun interface and vehicle charging interface are of the same type and can be plugged in smoothly.

2. Electrical parameter matching

The rated current, voltage and other electrical parameters of the charging cable, charging station and charging gun must be consistent with the vehicle charging requirements, and they can work safely with each other to avoid safety hazards caused by overload or mismatch.

3. Certification compliance

All components should comply with local electrical safety standards and regulatory requirements and have the necessary certification marks (such as CCC, UL, CE, etc.) to ensure product quality and safety of use.

4. After-sales service

Although the components are purchased separately, it is best to choose products from the same manufacturer or a cooperative manufacturer so that timely and effective technical support and after-sales service can be obtained when problems arise.

Conductor material of charging cable

The conductor material of charging station cable is mainly copper and aluminum. Copper conductors are widely used due to their excellent electrical conductivity and corrosion resistance, while aluminum conductors are used in some occasions due to their lower cost. When selecting cables, various factors should be considered comprehensively according to specific needs and use environment, and products with excellent performance and economy should be selected.