SiC Bidirectional Solid-State Circuit Breaker with Soft-Start Function for Motor Control Center

Solid-State Circuit Breaker (SSCB) has been identified as a potential game-changing technology for DC distribution. However, fewer SSCB research and applications have been reported in AC due to the direct competition with the conventional electromechanical circuit breaker, which has a proven record as AC circuit protection device. This paper investigates the current protection and soft start functions of a three-phase SSCB in the motor control center (MCC). The proposed SSCB integrates application-specific protection functions of soft starter, magnetic contactor, circuit breaker, and thermal relay. The paper designs and implements a three-phase SSCB with a rated voltage of 380VAC and a rated current of 63A. Three key design considerations, including semiconductor device selection, metal oxide varistor (MOV) and snubber selection, and heat sink selection are introduced. The current fault protection of the SSCB was tested and verified at 200A by a pulse test platform with a microsecond-level fault current clearing time. Finally, the soft start function was analyzed and realized without zero current detection. Both simulation and experimental results validate the soft-starting function with significant reduction of motor inrush current. By combining the conventional contactor, circuit breaker, and soft starter functions into one, SSCB can offer competitive advantages in MCC applications.