What are the main sources of interference when EFT exceeds limits in data center switches?

The main source of interference exceeding the EFT test limit in the data center switch originated from the transient switching of the primary MOSFET in the switching power supply and the parasitic coupling of the transformer. The frequency domain characteristic is a wide spectrum of 5kHz-100MHz with peak values concentrated in the 1MHz-30MHz range. Location method: A near-field magnetic field probe was used to scan the power module area, and the spectrum analyzer was set to RBW=9kHz and VBW=30kHz for peak detection. Rectification measures: Common-mode filtering at the power input was strengthened by adding a CMZ7060A-701T common-mode inductor (700Ω@100MHz) and increasing the Y capacitor from 1000pF to 2200pF; a 10Ω+470pF RC snubber was connected in parallel to the MOSFET's drain and source terminals to suppress ringing. After the rectification, the conducted emissions at the power port were reduced by 18-25dB in the 1MHz-30MHz band, passing the EFT±4kV test.