The ABB PR121/P 2500A circuit breaker is a low‑voltage air circuit breaker (ACB) from ABB’s SACE Emax / E3N/E3S series designed for heavy‑duty electrical distribution protection. It combines a PR121/P electronic trip unit with a breaker frame capable of handling continuous 2500 A current. The trip unit provides adjustable overload, short‑circuit, and earth‑fault protection functions to safeguard electrical feeders, busbars, and connected loads in commercial and industrial switchgear applications.