1. Radiated Interference: Radiated electromagnetic fields generated by space radiation are mainly produced by power grids, transient processes in electrical equipment, lightning, radio broadcasts, television, radar, high-frequency induction heating equipment, etc., and their distribution is very complex. If the PLC control cabinet supplier places the PLC system in its radio frequency field, it will be subject to radiated interference. This impact mainly occurs through two pathways: one is direct radiation within the PLC, which interferes with circuit induction; the other is radiation within the PLC communication network, which leads to induced interference in the communication lines.
2. Conducted Interference: This is interference from outside the PLC control cabinet system, mainly transmitted through power and signal lines, and is relatively frequent in industrial applications.
3. Power Supply Interference: The PLC system in the PLC control cabinet normally uses the mains power supply. As we know, the mains power supply has high coverage and a wide range. The characteristics of the mains power supply cause the PLC control cabinet to receive induced currents and voltages from spatial electromagnetic interference on the lines. When the mains power supply changes, it will also affect the PLC control cabinet. For example, surges from switching operations or transient impacts from mains short circuits will affect the mains power supply side of the PLC control cabinet. Therefore, the PLC control cabinet system will also experience interference.
4. Interference Introduced by Signal Lines: In addition to transmitting various types of information, there are external interference signals on the various signal transmission lines connected to the PLC control system. This interference has two main forms: one is mains power interference through the transmitter power supply or shared signal instrument power supply, which is often ignored; the other is interference from spatial electromagnetic radiation, i.e., external induced interference on the signal lines. Compared to the first type, this is more serious. Interference introduced by the signal can cause abnormal operation of I/O signals and a significant reduction in measurement accuracy. In severe cases, components will be damaged. For systems with poor isolation performance, signals can also interfere with each other, causing backflow on the common system bus, leading to changes in logic data, malfunctions, and crashes. It is not uncommon for PLC control cabinets to experience system failures due to signal interference.
