Does the length of PCS cables in an energy storage system affect radiation testing?

The length of PCS cable has a significant impact on its radiated emission (RE) test results. Cables, especially those that are not properly shielded or whose shielding is not properly grounded, are efficient radiating antennas. Their radiation intensity is related to the effective antenna length, typically reaching its highest efficiency when the cable length is 1/4 or 1/2 of the wavelength of the radiated noise frequency. Therefore, longer cables may generate efficient radiation at more frequencies, leading to worse RE test results.

Specific effects include:

1. Providing a radiating antenna: Providing a longer path for common-mode noise current, enhancing radiation.

2. Increasing resonant points: Longer cables will generate resonant peaks at lower frequencies. In EMC testing, standards often specify the use of typical cable lengths (e.g., 1 meter) to simulate real-world conditions and ensure comparability. Remedial measures, such as shortening cable length, improving shielding grounding, or adding ferrite cores to the cable, are common methods to reduce cable radiation.