不当接地引发的电磁干扰

电子系统与计算机进行仿真实验时发生电磁干扰;在排除电梯、车辆、电源线、信号线干扰对仿真实验的影响后,调查发现,电子系统和计算机分别由两组独立电源供电,每组电源都有接地桩,两个接地桩和信号地线围成面积约为300 m2的地回路;当实验接通电源的瞬间,瞬变电流在地回路内生成幅度很大的EMI信号,这是系统发生电磁干扰的真正原因.破坏掉这个地回路,可以实现仿真实验的正常运行.正确认识地回路与控制EMI的关系,对电缆敷设和接地设计有指导意义.

EMI Caused by Improper Grounding

An EMI was happened when a simulating test was going on between a computer and an electronic system is described in this paper. In order to know where the EMI came from, a lot of time was spent to remove EMI effect from elevator, vehicles, powerline and signal-line. Finally, it was found that the computer and electronic system were supplied by two independent power systems of TN-C-S grounding that must have their individual grounding stick. Then these grounding sticks and signal grounding formed a large grounding loop which was around 300 square meters. When the powers witch on, a big EMI signal was produced within the grounding loop and that destroyed the test. When the grounding loop removed, the simulating test was going on very well. From this lesson we should be very careful when designed cabling and wiring ground.