How to rectify EMC issues related to encoder signal distortion?

When encoder signal distortion (such as waveform distortion or glitches) occurs in the servo system, EMC rectification requires a systematic investigation. Yinte Electronics' rectification process:

1) Locate the interference source: Use an oscilloscope to observe the characteristics of the distorted waveform and use a near-field probe to scan the inside of the driver (such as IGBTs, DC buses) to find strong radiation sources.

2) Check the coupling path: Check whether the encoder cable is bundled parallel to the motor power line and whether the shielding layer is properly grounded.

3) Check the receiving circuit: Measure whether the common-mode choke (CML) at the receiving end is saturated, whether the TVS (ESD) is malfunctioning, and whether the filter capacitor is faulty.

Rectification measures:

a) Add a magnetic ring (PBZ series) to the encoder cable, winding 2-3 turns near the driver end.

b) Add an RC filter (such as 100Ω + 100pF) to the signal line at the receiving end.

c) Optimize the encoder power supply filtering by adding a PWR power inductor.

d) Ensure the shielding layer grounding impedance is <10mΩ.

Typically, the above steps can resolve most distortion issues, improve the signal-to-noise ratio (SNR) by more than 20dB, and restore stable operation.