控制系统中导线贯通屏蔽箱体对内部电路的影响

Impact of Conductor Penetrating Shielding Box via Apertures on Inside Circuit of Control System

运用时域有限差分法分析了屏蔽箱体的开口结构、位置方向等对屏蔽性能的影响,以及有贯通导线存在时,干扰电磁场对箱体内部电路耦合电流的影响。研究结果表明:当开孔面积一定时,开孔形状为矩形时的箱体屏蔽性能比较差,而开孔为圆形和正方形时屏蔽效果基本一样并都优于矩形开口;有导线贯通箱体时,箱体内部电路的耦合电流显著增大,且导线越长耦合电流越大。通过采用屏蔽环来抑制干扰发现,增加环的厚度可以降低干扰,而改变环的外环尺寸对抑制干扰效果不明显。

The impacts of apertures on shielding box, their positions and directions on shielding performance are analyzed by finite difference time domain （FDTD） method as well as the affects of electromagnetic interference on current coupled in the circuit inside the shielding box due to the conductor penetrating the box through apertures. Research results show that under a given area of apertures, the shielding performance of the box with the rectangular apertures is comparatively poorer while the shielding performance of the box with circular apertures is basically the same as that with quadrate apertures and both are better than that with rectangular apertures; when conductor penetrates the box thought apertures, the current induced in the circuit inside the box increases evidently, the longer the conductor, the larger the coupled current is. When shield ring is adopted to suppress the interference, it is seen that increasing the thickness of the ring can reduce the interference, however, the effect of interference suppression by changing the outer diameter of the ring cannot be obviously improved.