What impact does load have on EMC testing of industrial servos?

Load conditions (no load, half load, full load, different speeds and torques) significantly affect the EMC test results of servo systems. E-Tech Electronics' observations summarize:

1) Conducted interference: Generally, the larger the load, the greater the switching current amplitude, and the higher the amplitude of the low-frequency band (150k-1MHz) of conducted interference may be. Load changes may also alter the parasitic capacitance of the heatsink to ground, affecting common-mode noise.

2) Radiated interference: Motor speed and load changes alter the PWM modulation ratio and current waveform, thus affecting the distribution and amplitude of the radiated spectrum. Radiated noise may be more severe under high-speed, heavy-load conditions.

3) Immunity testing: Under full load, the system control loop is active and more sensitive to interference, potentially leading to torque fluctuations or overcurrent alarms.

Therefore, complete EMC testing should be conducted under various typical load conditions, especially the most severe conditions (such as maximum speed and maximum torque) to ensure the robustness of the product in practical applications. The load conditions during testing must be clearly recorded in the test report.