Lifetime Extension for Solid-State Circuit Breakers in Motor Control Center Applications

Solid-state circuit breakers (SSCBs) are becoming increasingly popular building blocks of direct current (DC) power systems due to their characteristics of fast interruption, arc-less operation, and no moving parts in recent years. However, the application of SSCBs in alternating current (AC) systems has been limited, primarily due to competition from traditional electromechanical circuit breakers commonly used for AC protection. This paper presents a comprehensive approach to integrate multiple functionalities, including soft start, overload relay, circuit breaker, and contactor, into a single three-phase bidirectional SSCB for motor control center (MCC) applications. This integration enhances system integration, intelligence, and significantly reduces the bulk compared to conventional MCC. In this paper, the lifetime performance of the SSCB is investigated, particularly its use as a contactor, and a turn-off solution is proposed to increase the lifetime and reliability of the SSCB without the participation of any voltage overshoot suppression or zero-crossing current detection devices. Furthermore, the proposed turn-off strategy is analyzed, and the design considerations for snubber and metal oxide varistor (MOV) selection are discussed in relation to the contactor function of the SSCB. Finally, simulation and experimental results are provided to verify the effectiveness of the contactor function and the proposed turn-off scheme.