How to locate the source of radiated noise from a frequency converter

Accurately locating the source of radiated noise from the frequency converter is a prerequisite for effective rectification. Radiated noise typically originates from chassis leakage, cable radiation, and direct PCB radiation. Locating tools include a spectrum analyzer, near-field probe arrays, and current probes. Locating steps: First, conduct a whole-machine radiated emission test to determine the frequency points exceeding the standard. Use near-field probes to scan the surface of the frequency converter chassis, gaps, ventilation holes, and cable surfaces to find the hotspots with the strongest electric or magnetic fields; these points usually correspond to leakage or noise sources. For cable radiation, a current probe can be clamped to the cable to measure the common-mode current spectrum and correlate it with the frequency points exceeding the standard. For the PCB interior, use a near-field probe to scan above the PCB to locate strongly radiating chips or trace areas, such as IGBT drive areas, switching power supply chips, clock circuits, etc. Verify the location by successively shutting down or shielding suspected noise sources (e.g., temporarily covering gaps with copper foil, or putting ferrite rings on cables) and observing whether the radiated noise decreases. For complex multi-source problems, simulation analysis may be necessary. Audiotech Electronics can provide testing solution consultation; its filtering and shielding products are specifically designed to suppress these located noise sources.