How does industrial servo soft switching improve EMC?

Soft-switching technologies (such as ZVS zero-voltage turn-on and ZCS zero-current turn-off) significantly reduce switching losses and di/dt and dv/dt by allowing power devices to switch when the voltage or current crosses zero, thereby improving EMC at its source. In servo systems, some soft-switching topologies (such as LLC resonant converters used in auxiliary power supplies) or the use of SiC MOSFETs with optimized drives can achieve similar effects. Real-world data from Eintec Electronics shows that auxiliary power supplies using soft switching can reduce conducted interference by 15-20 dB in the 1-10MHz frequency band compared to hard switching. For the main inverter, optimizing PWM modulation strategies (such as using SVPWM overmodulation or injecting third harmonics) can reduce the common-mode voltage amplitude, thereby reducing motor bearing current and common-mode EMI. Although soft switching may increase control complexity, the resulting EMC improvements are fundamental, helping the system pass Class B limits with smaller filters and improving efficiency by 1-3 percentage points.