Optimized Soft Starting of SiC MOSFET-Based Soft Starter with Constant Transient Current for Motor Control Center Applications

Fully-controlled power semiconductor device-based solid-state circuit breaker (SSCB) not only features fast fault interruption, arcless, noiseless, and no moving parts, but also has the capability to integrate functions of a soft starter, circuit breaker, contactor, and thermal relay in motor control center applications. This paper focuses on optimizing the soft start control method of SSCBs based on fully-controlled power semiconductors and proposes a constant transient current control strategy. Motor phase-to-neutral voltage and current expressions during the soft starting process are analyzed. Then, a transfer function is developed for the closed-loop control system with the effective value of motor current as a reference, along with its small-signal model. Furthermore, the control system stability and controller parameter selection are analyzed. Finally, the effectiveness of the proposed control solution is verified by both simulation and experimental results. The soft start time of the proposed solution is 5 s, which is less than half of the open-loop scheme’s 10.6 s, demonstrating a reduction of over 50% in soft start time.