Failure Analysis of PLCs Under High Power Electromagnetic Pulses

In this article, the failure mechanisms of programmable logic controllers (PLCs) under high power electromagnetic pulses (HPEMPs) are studied. The vulnerable ports, failure mechanisms, and sensitive parameters are studied theoretically and numerically, and the results indicate that PLCs may be damaged under external HPEMP. Input ports are more sensitive than output ports. Three high-speed counter ports I0.3, I0.4, and I0.5 may fail under HPEMP, resulting in the failure of the PLC to operate. The front components of these input ports are vulnerable. The heat generated through an electrothermal coupling process is the main failure reason. The welding point where the top wire of the diode connected to the bulk silicon is the main heat-generating area. The bottom electrode of the diode will also generate heat, which may cause the “popcorn effect,” ultimately leading to equipment failure. The numerical and experimental results show that the failure threshold voltage follows an exponential relationship (exponent of −2) with the width under quasi-static processes.