How does poor EPS grounding affect conducted emissions?

Poor EPS grounding can directly lead to excessive conducted emissions (CE) tests. The main mechanisms are as follows:

1. Filter failure: EMI filters (especially common-mode filters) rely on low-impedance grounding to function. Y capacitors need to conduct common-mode noise to the ground. If the grounding impedance is high, common-mode noise cannot be effectively bypassed and will flow directly to the LISN (Line Impedance Stabilized Network), resulting in excessive conduction.

2. Change in common-mode current path: Poor grounding forces common-mode noise current to find other unexpected paths to return, such as forming larger loops through input and output cables, increasing the efficiency of noise radiation and conduction.

3. Increased ground noise: The impedance of the common grounding point will increase power ground noise. This noise may couple to signal lines through parasitic capacitance or be conducted directly through the grounding wire.

4. Reduced shielding effectiveness: If the cable shielding layer and cabinet are poorly grounded, their shielding effect will be greatly reduced, allowing external interference to enter and internal noise to escape. Therefore, low-impedance grounding is the foundation for achieving conduction compliance.