How to locate the source of radiated noise in industrial servo systems?

Accurately locating the radiated noise source of the servo system is a prerequisite for efficient rectification. Audiotech's location methods include:

1) Using a near-field probe kit: Place a magnetic field probe near power circuits (such as IGBTs, DC buses), driver chips, clock circuits, etc., on the PCB. Use an electric field probe to scan gaps and cable interfaces, and observe with a spectrum analyzer which location's noise amplitude matches the exceeding frequency point of the far-field test.

2) Using a current probe: Clamp it to the motor cable and power line, measure the common-mode current spectrum, and determine if the cable is the main radiating antenna.

3) Step-by-step isolation method: While the system is running, disconnect the motor cable, encoder cable, and communication cable in sequence, observe the changes in far-field radiation, and locate the main radiation path.

4) Temporary shielding test method: Temporarily cover the suspected area (such as heat sinks, gaps) with copper foil and observe whether the radiation decreases.

Typically, motor cables, poorly filtered DC buses, and cabinet gaps are the main radiation sources. After locating the source, targeted strengthening of filtering, shielding, or grounding can be implemented.