How to control common-mode conducted interference in power FTUs?

Common-mode conducted interference mainly enters the FTU system through power lines and signal lines. The solution employs a multi-stage common-mode filtering architecture. A CMZ7060A-701T series high-current common-mode inductor (700μH) is installed at the power input, along with a CY-Y5P-222K safety-certified Y capacitor (2.2nF/250V), forming the first stage of filtering. A CML4532A-510T common-mode inductor (510μH) is used for the second stage of filtering on the secondary power supply side. A CMZ2012A-900T series common-mode inductor (90μH) is used at the signal interface, along with an ESDLC3V3D3B low-capacitance ESD protection device. The grounding system uses a star-connected single-point grounding configuration with a grounding wire impedance of less than 0.1Ω. With this solution, common-mode conducted interference can be attenuated by more than 40dB in the 150kHz-30MHz frequency band, meeting the EN55032 Class B limit requirements and passing the IEC 61000-4-6 conducted immunity test (10V).