How to balance EMC/safety requirements in motion controller MCX/Y capacitors?

In motion controllers (MC), the configuration of X and Y capacitors must simultaneously meet EMC filtering requirements and safety standards. The X capacitor, connected between the L and N lines, is used for differential-mode filtering. Its capacitance value is selected based on the noise frequency to be attenuated, commonly ranging from 0.1μF to 2.2μF. A discharge resistor must be connected in parallel to ensure the voltage drops below the safe voltage within one second after power failure. The Y capacitor, connected between the L-PE or N-PE lines, is used for common-mode filtering. Its capacitance value is limited by the allowable leakage current, typically not exceeding 4.7nF. Safety-certified Y1 or Y2 grade capacitors must be selected. A Y capacitor is also required between the DC bus and the chassis ground. All safety capacitors should be placed as close as possible to noise sources, such as between the primary and secondary sides of the transformer in a switching power supply. On the PCB layout, capacitor leads should have short and thick traces to reduce parasitic inductance. After configuration, a leakage current test must be performed to ensure compliance with safety standards. In EMC testing, the conducted emissions are verified to meet standards. If not, the X capacitor value can be adjusted appropriately, but the leakage current and discharge time must be reassessed.