Electronic MOV-Based Voltage Clamping Circuit for DC Solid-State Circuit Breaker Applications

Traditional metal oxide varistor (MOV) based voltage clamping circuits (VCC) used in solid-state circuit breakers reduce the efficiency of the system due to the high voltage requirement imposed on the main solid-state device. The voltage burden arises from the material properties of the MOV which fixes its clamping voltage at a value more than twice its maximum continuous dc voltage rating. This letter proposes a novel and reliable VCC termed as the electronic MOV (eMOV) to altogether decouple the peak clamping voltage of the MOV from the nominal dc voltage of the system aiming to improve the voltage suppression index (VSI = V-pk/V-dc) of the VCC, thereby reducing the system conduction losses. The eMOV introduces a breakover diode to share the system dc voltage during the standby state and a Silicon controlled rectifier to provide the bypass path for the fault current for quick MOV insertion. Comprehensive design criteria are developed to guide the component selection and overall design. Experimental results at 2 kV dc and 1.1 kA peak current are presented to validate the operation of the proposed eMOV based VCC.