The Impact of Solid-State Technology on Molded Case Circuit Breakers

Molded case circuit breakers with solid-state trip units have been widely applied in industrial power systems for more than a decade. Today's Underwriters Laboratories (UL) listed molded case circuit breakers offer the application engineer many versatile features for systems selectivity such as high short-circuit interruption, high short-time ratings, integral ground fault protection, stored energy mechanisms, versatile mounting arrangements, manual or electrical operation, zone selective interlocking, and fault indicators. The development and application of solid-state technology in molded case circuit breakers are briefly traced, explaining the features and how they can be used.