How to rectify substandard industrial servo conduction transmitters?

When the conducted emission (CE) test of the servo system fails, systematic location and rectification are required. The rectification process for Yinte Electronics is as follows:

1) Analyze the spectrum: Identify whether the out-of-specification frequency is discrete (switching frequency harmonics) or continuous (broadband noise), and determine whether the out-of-specification is common-mode or differential-mode (by comparing the phase/neutral voltage of the LISN).

2) Targeted rectification: If the differential-mode out-of-specification is in the low-frequency range (150k-1MHz), increase the capacitance of the X capacitor or add a differential-mode inductor (PWR series). If the common-mode out-of-specification is in the mid-to-high frequency range (1M-30MHz), enhance the common-mode filtering: replace with a common-mode inductor with a higher inductance or higher frequency impedance (such as the CMZ series), adjust the Y capacitor value (usually try between 1nF-4.7nF), and check if the Y capacitor is properly grounded.

3) Check the noise source: Ensure the IGBT buffer circuit and drive resistor parameters are reasonable.

4) Optimize the PCB layout: Check if the filter is close to the noise source and if the grounding is low impedance.

After rectification and retesting, the frequency points exceeding the standard can usually be reduced by 10-20dB until the limit requirements are met.