How to ensure EMC (Electronic Performance Measurement) of a PMS (Power Measurement System) under full load?

When a power supply system (PMS) operates at full load (rated voltage and current), its internal power devices experience maximum heat generation and current stress, and its EMC condition may differ from that under light load. Ensuring EMC performance under full load requires targeted design. First, the rated current of power filtering components (such as the common-mode inductor CMZ1211-501T) must be greater than the full-load current, and performance degradation due to temperature rise should be considered; typically, a current margin of 50% or more should be chosen. Second, the ripple and noise of the switching power supply may increase under full load. It is necessary to ensure that the ESR of the output filter capacitors (especially electrolytic capacitors) remains sufficiently low at high temperatures; multiple ceramic capacitors can be connected in parallel.

PCB layout must consider the impact of heat generation from high-current paths on adjacent sensitive circuits, adding thermal insulation or physical isolation as necessary. During EMC testing, full-load testing is essential because some radiated emissions may only appear under specific load currents. Simultaneously, it is crucial to monitor whether the metering accuracy still meets requirements under full load, as thermal noise and ground noise may increase. Through design and testing verification, it is ensured that the PMS's EMC performance fully meets standards and that metering accuracy remains stable at 100% load.