Novel Active Snubbers for SSCBs to Improve Switch Voltage Utilization Rate

This article proposes two novel active snubbers for direct current (dc) solid-state circuit breakers (SSCBs): metal-oxide-varistor with resistor–capacitor-switch (MOV-RCS) and active-MOV with resistor–capacitor–diode (AMOV-RCD). In the snubber branch, either a half- or full-controlled switch can be applicable, leading to four novel topologies. There are two main contributions: 1) MOV is disconnected from the power line during SSCB OFF-state, which enhances reliability as neither voltage nor power appears on MOV and 2) voltage utilization rate
$\eta _{v}$
of the main switch is remarkably increased, which improves efficiency and power density, and reduces design cost. Experiments of five prototypes are conducted including four proposed snubbers and a comparison with conventional MOV-RCD snubber. Results show that, for 1.2-kV MOSFETs as the main switch, new snubbers can enhance
$\eta _ {v}$
from 37.5% to 60%, achieving 183-A dc current interruption under 720-V dc bus voltage within
$2.4~\mu \text{s}$
. Meanwhile, the voltage peak is limited to 1.112 kV.