How are the working ground and protected ground of a smart controller PAC separated?

In a PAC (Power Control Controller), proper separation of the working ground and protective ground is crucial for suppressing common-mode interference and ensuring safety. The working ground (signal ground) serves as the circuit's reference zero potential, while the protective ground (safety ground) is used for chassis shielding and leakage current discharge. The separation principle is as follows: On the PCB, the working ground and protective ground are connected at a single point via a ferrite bead (such as PBZ1608A-102Z0T) or a 0Ω resistor, with the connection point chosen near the power input port. The chassis protective ground is directly connected to earth via a low-impedance path (such as a metal bracket or conductive foam).

For high-frequency noise, a Y capacitor (such as 2.2nF/250VAC) can be connected in parallel at the separation point to provide a high-frequency path. During layout, the working ground plane should be complete and avoid being separated by the protective ground. The protective ground surrounds the PCB and is connected to the metal chassis through multiple vias. Tests have shown that this separation scheme can reduce the impedance between the working ground and protective ground to less than 1Ω at 10MHz, attenuate common-mode noise by more than 30dB, and meet the IEC60950-1 safety clearance requirements.