What's the point of adding a high-flex cable shield?

Author: EVCOME-EV Chargers Manufacturers

As we all know, there is a big difference between shielded cables and unshielded cables. Obviously, the effect of shielding and anti-signal interference is better. What are the benefits of flex cable shielding? Shielded cable is a special type of cable that shields insulation around the cable to reduce electromagnetic interference (EMI), allowing external electromagnetic and magnetic field radiation to pass directly into the ground without disturbing the internal wires. The shielding layer of ordinary shielded cables is woven into a net shape by tinned copper, and the conductor insulation is covered to form a shield. When an electromagnetic field with a high external frequency passes through the shielding layer, eddy currents and losses will be generated, thereby exerting an anti-interference effect and ensuring safe and stable transmission of signals in the cable. The shielded cable with two shielding layers is also called double-shielded cable. The mesh braiding layer prevents magnetic field radiation, and tinned copper is generally used as the braiding material; the aluminum foil layer is used to prevent electromagnetic radiation. More importantly, the shield must be fully grounded to effectively direct interference currents to ground. The shielding significance of flexible cables needs to start with EMC electromagnetic compatibility. For example, signal cables or control cables are weak electrical signals and are susceptible to interference. Therefore, in most cases, the signal cable or control cable is shielded; but in a few cases, the signal cable or control cable does not need to be shielded, so there is a condition: the nearby electromagnetic environment is very clean. Many people think that power cables do not need shielding. For the power cable, due to the strong current, it is not afraid of interference, so there is no need to shield the power cable itself. However, if electromagnetically sensitive equipment or components are distributed around the power cable site, shielded power cables should be selected to prevent electromagnetic radiation from interfering with other equipment or components around the power cable. The shielded cable shield is grounded. There are usually two ways to ground the shielding layer: single-ended grounding and double-ended grounding. The single-ended grounding of the shielding layer is to directly ground the metal shielding layer at one end of the shielded cable.——terminal is not grounded or grounded through protection. When the shielding layer is grounded at one end, there is an induced voltage between the ungrounded metal shielding layer and the ground, which is proportional to the length of the cable, but the shielding layer has no potential circulation. Single-ended grounding eliminates electromagnetic interference by suppressing potential differences. This grounding method is suitable for short-term use, and the induced voltage corresponding to the length of the cable must not exceed the safe voltage. The existence of electrostatic induction voltage will affect the stability of the circuit signal, and sometimes it may be the antenna effect. Double-ended grounding is the grounding at both ends of the metal shielding layer of the shielded cable. Purpose of shielding cable tape. Shielding is to ensure the transmission performance of the system in the environment of electromagnetic interference. The anti-interference here should include two aspects, namely the ability to resist external electromagnetic interference and the ability of the system itself to radiate electromagnetic interference. In theory, wrapping a metal shield around the outside of the cables and connectors can effectively filter out unwanted electromagnetic waves (this is also the method used by most shielding systems). But how effective is this approach? For shielded systems, a metal shield alone is not enough. More importantly, the shield must be fully grounded to effectively direct interference currents to ground. However, in actual construction, there are some difficulties in the shielding system that cannot be ignored: due to the strict requirements of the shielding system on grounding, such as excessive grounding resistance, unbalanced grounding potential, etc., it is easy to cause poor grounding. In this way, a potential difference will be generated between two points of the transmission system, which will cause a current on the metal shield, causing a discontinuity in the shield and destroying its integrity. At this point, the shielding layer itself has become the biggest source of interference, and its performance is much lower than that of an unshielded system. The shielded wire needs to be grounded at both ends during high-frequency transmission, so it is more likely to generate a potential difference across the shield. It can be seen that the requirements of the shielding system itself are the biggest obstacle to ensuring its performance. A complete shielding system requires shielding everywhere. Once any shielding fails to meet the requirements, the overall transmission performance of the system will inevitably be affected. But in the market. Few network hubs or computers themselves have shielding support, so it is difficult to shield the entire transmission link. .


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