How to suppress EFT common-mode interference in data center switches?

EFT interference from data center switches is injected into cables in common mode. The key to suppression is to reduce common-mode impedance and provide a low discharge path.

Power port solution: A series CMZ7060A-701T common-mode inductor (700Ω@100MHz) from Etymotic is used to block common-mode current, and a 2200pF/400VAC Y capacitor is connected in parallel across L/N-PE to provide a return path.

Signal port solution: A series PBZ1608A-102Z0T ferrite bead (1000Ω@100MHz) is used to absorb common-mode energy, and a 1000pF/2kV high-voltage capacitor is connected in parallel to ground from the transformer center tap.

PCB layout requires a spacing of <5mm between the common-mode inductor and the Y capacitor, and a grounding impedance of <10mΩ. Measured common-mode rejection ratio (CMRR) is >40dB in the 1MHz-100MHz frequency band, and the residual voltage at the port is <8V when EFT ±4kV is injected.