How does the carrier frequency of an industrial servo motor affect EMC?

The servo carrier frequency (PWM switching frequency) directly affects the EMI spectrum distribution and amplitude. Higher frequencies increase switching losses and dv/dt, leading to increased radiated interference in high-frequency bands (e.g., above 30MHz); lower frequencies may result in larger fundamental and harmonic amplitudes in conducted interference in low-frequency bands (150kHz-30MHz).

Based on measured data, E-Tech Electronics recommends: for common 4kHz-16kHz carriers, enhanced differential-mode filtering is needed in the conducted band, using a combination of CMZ3225A-201T (200μH) and X2 capacitors (0.22μF); in the radiated band, optimized motor cable shielding is needed, with the addition of PBZ2012E-220Z0T ferrite beads (220Ω) at the line terminals. When the carrier frequency exceeds 10kHz, special attention should be paid to ESD protection of the IGBT drive circuit, using ESD SRV05-4H. Frequency sweep testing revealed that after optimization at an 8kHz carrier, the system meets CISPR 11 Class A limits, with a total harmonic distortion (THD) of <3%. The design process requires balancing EMC performance with motor noise and efficiency.