Technical Parameters Parameter Specification Product Name ABB PR121/P 1250 A Air Circuit Breaker Model / Variants E1N / E2N / E3S series with PR121/P trip unit Product Type Low‑Voltage Air Circuit Breaker (ACB) Protection Unit PR121/P electronic trip unit Rated Current (I_n) 1250 A Rated Uninterrupted Current (I_u) 1250 A Number of Poles 3 pole (3P); 4 pole available in some variants Rated Operational Voltage (U_e) Up to 690 V AC Rated Insulation Voltage (U_i) 1000 V AC Rated Impulse Withstand Voltage (U_imp) 12 kV (typical design for low‑voltage breakers) Short‑Circuit Breaking Capacity (I_cu) Typically ~42 kA – 65 kA at 400 V AC depending on frame and configuration Short‑Time Withstand Current (I_cw) Varies by model; e.g., ~42 kA for 1 s or ~55 kA for 1 s Overload Release Setting ~500 A – 1250 A adjustable Short‑Circuit Adjustable Ranges Short‑time and instantaneous ranges up to several multiples of In Protection Functions Long‑time (L), short‑time (S), instantaneous (I), earth fault (G) Auxiliary Contacts Yes (change‑over contacts standard on many variants) Mounting Type Fixed frame (rear horizontal or withdrawable moving parts depending on series) Control / Indication Breaker trip and position indication available Typical Use Main feeder protection, distribution boards, switchgear protection