How can the onboard filter of the power measurement switch (PMS) be adapted to high voltage?

When the onboard filter circuit of the PMS is directly connected to high voltage (e.g., 400VAC), it must simultaneously address high voltage safety, high current stress, and high-frequency interference, posing a significant design challenge. The key to successful adaptation lies in component selection, insulation layout, and thermal management. First, the filter components must meet the withstand voltage and safety requirements of high voltage: X capacitors should be X2 class (≥275VAC), Y capacitors should be Y1 class (≥300VAC), and the interlayer insulation of the common-mode inductor CMZ1211-501T must meet reinforced insulation (e.g., 4kV). In terms of PCB layout, the creepage distance and clearance between high-voltage areas (L, N, PE) and other areas must comply with IEC 60664-1 standards (e.g., greater than 5.5mm for 400VAC).

The filter circuit should be centrally located at the power input on the board edge and isolated from low-voltage areas by slots. To handle high current heat generation, the differential-mode inductor PBZ3216E120Z0T should use an iron-silicon-aluminum core with a saturation current greater than 30A. Meanwhile, considering thermal coupling, copper is laid under the inductor and heat dissipation vias are added. With adaptive design, the onboard filter circuit can operate continuously in an environment of -40°C to 85°C, withstand 4kV surge impact, and suppress conducted interference within the limits of EN 55032 Class A.