【電磁技術(shù)在線】【EMC篇】- 3. 線纜屏蔽

講師：Andreas Barchanski

00：00 汽車EMC挑戰(zhàn)，線纜

04：30 單獨(dú)線纜案例

05：40 無(wú)限尺寸屏蔽墻

09：20 有限尺寸屏蔽墻

14：10 一對(duì)或多組線纜案例

In this video, you will learn a lot about the shielding simulation, especially what kind of material model should be used in designing and simulating the shielding of cables. 

A shielded cable or screened cable is an electrical cable of one or more insulated conductors enclosed by a common conductive layer. The shield may be composed of braided strands of copper (or other metal, such as aluminium), a non-braided spiral winding of copper tape, or a layer of conducting polymer. Usually this shield is covered with a jacket.

The shield acts as a Faraday cage to reduce electrical noise from affecting the signals, and to reduce electromagnetic radiation that may interfere with other devices (see electromagnetic interference). The shield minimizes capacitively coupled noise from other electrical sources. The shield must be grounded to be effective.[1] The shield should be electrically continuous to maximize effectiveness, which includes cables splices.

Eddy Current Shielding:

• A time variant magnetic field induces current in the conductive material

• Induced currents are of opposite direction to the source current

• Induced current create magnetic fields opposite to the direction of source field

• Net field is reduced -> this is what we call shielding

• Induced current is frequency depended -> Higher shielding at higher frequencies

Permeable Shielding

• Permeable material affects magnetic field distribution

• Effectis not frequency depended but permeability also affects skin depth

• No shielding for magnetic field tangential to material surface

Simulation offers insight into the mechanisms involved in shielding of low-frequency magnetic fields. The challenges include choosing between Eddy current and permeable shielding, as well as finite shield size. Low impedance shield bonding is crucial and moving main conductors close together is very efficient. Parameter studies allow to estimate the required thickness, material and laying of the cables