How to reduce EMI from DV/DT overshoot in frequency converters

To reduce EMI caused by dv/dt overshoot in frequency converters, the key lies in mitigating the voltage change rate during IGBT switching and absorbing oscillations. Excessive dv/dt generates strong common-mode current through the parasitic capacitance of the motor cable, exciting cable resonance and causing radiation. Optimization begins with the drive circuit. Connecting a diode in parallel with the gate resistor or using an active Miller clamp circuit appropriately slows the voltage rise rate during turn-off, but switching losses must be balanced. Connecting a high-frequency absorption capacitor, such as a dedicated dv/dt absorption capacitor, directly in parallel between the IGBT's collector and emitter effectively reduces voltage spikes and rise rates.

Using an RC snubber circuit across the IGBT dampens resonance caused by stray inductance and absorption capacitors. A common-mode choke and dv/dt filter are installed on the output side specifically to filter out high-frequency common-mode noise from the motor lines. Structurally, ensuring good contact between the IGBT module and the heatsink, and using low-impedance grounding, allows the heatsink to act as a shield and absorber for high-frequency noise. Optimizing the absorption element parameters through simulation and testing ensures a balance between EMI and efficiency. The series of absorption capacitors and RC components provided by Eintech Electronics are key components for building efficient dv/dt suppression solutions, which can significantly reduce the EMI problems caused by them.