Comparative Study of Solid State Circuit Breakers for Large Inductive Loads

The utilisation of solid-state circuit breakers (SSCBs) for managing large inductive loads with rated or short-circuit currents often results in overvoltage issues in the power switch, leading to potential failure. To mitigate this overvoltage, the addition of an extra electronic circuit is necessary. The main techniques typically fall into two categories: snubber-based and voltage-clamped. The snubber-based circuits are the best suited for the considered application; the RCD (Resistor, Capacitor, diode) snubber circuit adds the zero voltage switching but reduces the interruption capability compared to the RC (Resistor, Capacitor). Both snubber circuits are compared with the voltage-clamped SSCB. It is verified that the RC- and RCD-based SSCB reduce the stress for the power switch and guarantee a reduced overvoltage if the capacitance is properly sized. Conversely, the voltage-clamped solution reduces the current interruption capability for thermal limits, but does not suffer from overvoltage problems. This paper outlines guidelines for selecting the values of the RC and RCD snubber components and presents a graphical analysis of a case study involving a large inductive load, with variations in some design parameters.