Wiring Best Practices for Servo Systems – Noise Immunity Guide
The Grounding Golden Rule
Servo drives generate high-frequency electrical noise that can corrupt PLC inputs or encoder signals. Always use a single-point ground for the entire control cabinet—connect the drive's PE (Protective Earth) terminal directly to the main grounding bar. Avoid daisy-chaining grounds, as this creates ground loops. For Siemens V90 drives, the manual explicitly recommends a separate earth cable no longer than 3 meters.

Cable Separation and Shielding
Separate power cables (motor and mains) from signal cables (encoder and I/O) by at least 10cm. Use twisted-pair shielded cables for the encoder feedback and connect the shield to ground at both ends for frequencies above 1MHz. For Schneider LXM32 drives, the shield clamp must touch bare metal on the drive housing. Never run servo motor cables parallel to PLC communication lines—cross them at 90-degree angles if unavoidable.

Practical Checks After Wiring
After installation, measure the leakage current on the PE cable—if it exceeds 30mA, you may need an EMI filter. Power up the system without the motor connected first and check for any false triggers on proximity sensors. For Omron servos, use the built-in oscilloscope function to monitor encoder signal integrity; any jitter above 50mV indicates poor shielding and needs immediate correction.

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