In modern industry, communication and power transmission, seven-core cables are widely used in complex environments. In order to ensure the stability of signal transmission and the integrity of data, shielding design has become an important part of seven-core cables. Electromagnetic interference (EMI) is the main problem affecting cable performance. Shielding technology effectively improves the anti-interference ability of cables by suppressing the interference of external electromagnetic waves and internal signal leakage. This article will explore the shielding design principle of seven-core cables and its role in reducing EMI.

1. Sources of electromagnetic interference and their hazards
Sources of EMI

External interference: High-frequency electromagnetic waves from motors, inverters, radio equipment and other equipment can interfere with the signal transmission of cables.
Internal interference: Crosstalk may occur between different cores in seven-core cables due to signal crossing or power fluctuations.
Hazards of EMI

Signal distortion or loss, resulting in data transmission errors.
Equipment performance is reduced and may even cause equipment damage.
Communication delays or interruptions have a significant impact on industrial automation systems.
2. Basic principles of seven-core cable shielding design
The shielding layer is a protective structure wrapped around the conductor or core group. Its function is to block external electromagnetic interference and limit the radiation of internal signals to the outside world. Shielding materials usually have good conductivity and reflectivity to achieve the following functions:

Reflection interference: The external electromagnetic waves are reflected back to the source through the shielding layer to prevent them from entering the cable.
Absorption interference: The shielding layer material can absorb part of the electromagnetic wave energy and reduce the interference intensity.
Grounding drainage: The interference current is guided to the grounding device through the shielding layer to protect the signal integrity.
3. Common shielding types of seven-core cables
Braided shielding

Structure: Braided by copper or tinned copper wire to form a shielding layer with a coverage rate of more than 85%.
Features: Strong resistance to mechanical damage, suitable for mobile environments or scenes with more mechanical friction.
Advantages: Provide good electromagnetic shielding effect while maintaining the flexibility of the cable.
Aluminum foil shielding

Structure: Composited with aluminum foil layer and plastic film, usually used with drainage wire.
Features: Excellent shielding effect for high-frequency interference, light and low cost.
Application: Suitable for static applications or high-frequency signal transmission scenarios.
Double shielding

Structure: Combine the braided layer and the aluminum foil layer to form a double-layer shielding structure.
Features: It has the ability to shield both high-frequency and low-frequency interference, and has excellent anti-interference performance.
Application: Suitable for complex industrial environments that require high signal integrity.
Shielded core pair design

Structure: Independently shield each pair of core wires to further reduce crosstalk between pairs.
Features: Suitable for scenarios with high-density signal transmission in multi-core cables.
4. Advantages of shielding design in reducing EMI
Reduce the impact of external interference on signals

The shielding layer can block electromagnetic waves from surrounding equipment, protect signal transmission from interference, and maintain high reliability of transmission.
Suppress crosstalk of internal signals

The independent shielding design reduces mutual interference between the core wires inside the cable, ensuring the signal independence and stability of each core wire.
Prevent signal leakage

The shielding layer limits the outward radiation of cable signals, avoids interference with surrounding equipment, and improves information security.
Enhanced anti-interference performance

Double shielding or high-coverage braided shielding can effectively suppress high-frequency and low-frequency electromagnetic interference in complex environments and meet stringent industrial requirements.