How to coordinate SPD of frequency converter with EMC grounding

Surge protectors in inverter systems need to work in conjunction with the EMC grounding system to effectively discharge energy from lightning strikes or operational overvoltages without affecting normal EMC performance. The SPD's grounding must be low-impedance and reliable; the cross-sectional area and length of its grounding conductor must meet surge current discharge requirements, typically requiring it to be short and thick. The SPD should be installed at the incoming port, and its grounding wire should be directly connected to the cabinet's grounding busbar or independent grounding post, avoiding long-distance detours. The SPD's protection mode (e.g., L-PE, N-PE) must be matched to the power supply system. At the EMC level, an SPD generates a rapid, large current pulse upon operation, potentially causing a momentary high potential rise on the ground wire. Therefore, the SPD's grounding path should be separated from the grounding path of sensitive circuits as much as possible, or ensure that the sensitive equipment and the SPD grounding point are in a good equipotential bonding state. Sometimes, a decoupling inductor or two-stage SPDs need to be used between the SPD and the equipment. The installation of the SPD should not disrupt the continuity of the cable shield. Selecting an SPD with low residual voltage and fast response helps reduce the impact on downstream equipment. With proper installation and grounding planning, SPDs can coexist harmoniously with the EMC filtering and shielding measures of frequency converters, jointly ensuring system safety.