The ABB SACE Emax PR121/P is a trip unit / protection release designed for use with ABB SACE Emax series low-voltage air circuit breakers. It is a microprocessor-based, self-powered electronic protection module that integrates multiple protection functions into one unit. The PR121/P monitors current and provides overload, short-circuit, instantaneous short-circuit, and optional earth-fault protection, depending on configuration. It is installed directly on Emax breakers (3-pole or 4-pole, with or without neutral) and controls the breaker’s trip mechanism to interrupt the circuit when a trip condition is detected. The unit also provides LED indicators for alarm/trip status and allows parameter setup via DIP switches or external configuration tools
