How to control common-mode conducted interference in intelligent low-voltage monitoring units?

Common-mode conducted interference control employs a multi-stage common-mode filter network. The power input uses a CMZ3225A-510T common-mode inductor (510μH) paired with a CY-Y1-222K Y capacitor (2.2nF/250V). The secondary power supply side uses a CML4532A-101T common-mode inductor (100μH). The signal interface uses a CMZ2012A-900T series common-mode inductor (90μH). The grounding system uses a single-point star ground with a grounding impedance of less than 0.05Ω. PCB design: the common-mode inductor is placed close to the interference source, with a complete ground plane underneath. With this control scheme, common-mode conducted interference is attenuated by more than 35dB in the 150kHz-30MHz frequency band, meeting the EN55032 Class B conducted emission limits and passing the IEC 61000-4-6 10V conducted immunity test.