How to balance EMC and safety insulation requirements for edge computing boxes?

Edge computing boxes require Y capacitors to bridge the primary and secondary sides or PE and signal ground to discharge high-frequency common-mode current. However, safety standard IEC62368-1 limits contact current, thus limiting the total capacitance of Y capacitors, typically <4.7nF 250V. A compromise is found using:

1) High-voltage ceramic Y capacitors, 2kV, 1000pF per capacitor;

2) Increase the number of Y capacitors, but the total capacitance must not exceed the limit;

3) Use digital isolators with a withstand voltage of 5kV at the signal isolation point to achieve EMC filtering and meet reinforced insulation requirements;

4) The power transformer should have double insulation or reinforced insulation to meet creepage distance requirements, while Y capacitors bridge the primary and secondary sides.

Edge box design should select safety-certified Y capacitors, such as the Y series from Etymotic, to simultaneously meet EMC filtering and safety insulation requirements. The L/N and PE slot width on the PCB should be >2mm. A measured product had a leakage current of 0.18mA, and the Y capacitor was 1nF 2kV, passing EFT 4kV and withstand voltage tests.