How to suppress circulating current when industrial servo devices are connected in parallel?

When power devices (such as IGBT modules) are connected in parallel in a servo system, dynamic and static circulating currents can occur due to inconsistent parameters and asymmetrical layout, leading to uneven current distribution, additional losses, and potentially oscillations. Audiotronics' suppression measures include:

1) Static current sharing: Selecting devices with matched Vce(sat) and Vth (error <5%).

2) Dynamic current sharing: Connecting an independent resistor (Rg) in series with the gate of each device and ensuring symmetrical wiring. Connecting a small inductor (such as a few nH PCB trace inductor) or a ferrite bead (PBZ1608A-102Z0T) in series on the emitter lead to increase the unbalanced impedance.

3) Symmetrical layout: Ensuring the path length and impedance from the DC bus to each module are identical, using symmetrical stacked busbars.

4) Drive isolation: Providing an independent drive signal for each parallel device or using a dedicated current sharing drive IC.

These measures can control the dynamic current imbalance between parallel devices to within 10%, avoiding localized overheating and abnormal sideband noise in the EMI spectrum caused by circulating currents.