The impact of electromagnetic interference

- May 13, 2018-

In the modern industrial control system, the microcomputer or PLC control technology is often used. In the process of system design or modification, the interference problem of the Mitsubishi inverter to the microcomputer control board must be paid attention to. The external interference source of Mitsubishi inverter is shown in Figure 1. Since the user's own designed microcomputer control board generally has poor process level and does not comply with EMC international standards, the conduction and radiation interference generated after using Mitsubishi inverter often leads to the control system. The work is abnormal, so the necessary measures described below are required.

Good grounding. The grounding wire of the strong electric control system such as the motor must be reliably grounded through the grounding busbar, and the shielding ground of the microcomputer control board should be grounded separately. For some severe interference situations, it is recommended to connect the sensor and I/0 interface shielding layer to the control ground of the control board.

Adding power to the microcomputer control board to install EMI filter, common mode inductor, high frequency magnetic ring, etc., can effectively suppress conducted interference. In addition, in the case of severe radiation interference, such as the presence of GSM or PHS base stations, a metal mesh shield can be added to the microcomputer control board for shielding.