How to reduce EMI in industrial servo DV/DT overshoot?

In servo systems, dv/dt overshoot is primarily caused by voltage spikes when the IGBT is turned off. Its high-frequency components radiate through the motor cable and couple to the control circuit. The key to reducing this type of EMI is to slow down the rate of voltage change and absorb high-frequency energy. Audiotech recommends a combination of a buffer circuit and a ferrite bead: an RCD buffer circuit with a 22Ω resistor and a 100pF/1kV C0G capacitor is connected in parallel between the IGBT collector and emitter; simultaneously, a PBZ2012E-220Z0T ferrite bead (220Ω@100MHz) is connected in series on the motor output line to suppress high-frequency radiation.

For the drive signal, an ESDLC5V0D8B low-capacitance TVS protector is used to protect the gate. Actual measurements show that this solution can reduce dv/dt from 15V/ns to below 5V/ns, correspondingly reducing radiated interference in the 30-100MHz frequency band by 6-10dB. During layout, the buffer circuit should be placed close to the IGBT pins, and the ferrite bead should be installed near the motor terminals to ensure the shortest path. This design complies with IEC 61000-6-4 industrial launch standard.