Technical Parameters Parameter Specification Manufacturer ABB Model / Type PR121/P‑LSIG Product Category Electronic Overcurrent Trip Unit Application Protection for compatible ABB low‑voltage air circuit breakers Protection Functions • L – Long‑time overload protection • S – Short‑time delayed overcurrent protection • I – Instantaneous short‑circuit protection • G – Ground fault (residual) protection Adjustability Adjustable pickup levels and time settings for L, S, I, and G zones Trip Output Drives breaker trip coil to open the breaker under fault conditions User Interface Front‑panel adjustment dials or DIP switches / software configuration (model dependent) Indication LED or display status indicators for protection state and trip cause Auxiliary / Control Supply Typically requires an auxiliary/control supply (AC or DC) to power the electronics and indicators (voltage range depends on breaker platform) Poles Protected 3‑phase (L1, L2, L3) Frequency 50/60 Hz compatible Operating Environment Electrical switchgear and distribution panels Mounting Installed within the breaker protection slot/interface of compatible ABB ACBs Standards Compliance Designed to meet international low‑voltage overcurrent protection standards Typical Supported Breaker Ratings Commonly used with breakers from mid‑range to high‑current frames (e.g., several hundred to several thousand amperes depending on breaker model) Communication / Monitoring (optional) Some implementations support remote signaling or communication via breaker platform interfaces