The ABB E4N 4000 T LSI 3‑pole Air Circuit Breaker is a high‑capacity low‑voltage protective device from ABB’s Emax E4N series designed for three‑phase industrial and commercial power distribution systems. It combines a rugged breaker frame with an electronic protection trip unit (LSI) that provides coordinated and adjustable protection against overloads, short‑time faults, and instantaneous short circuits. The breaker comes with both fixed horizontal rear (FHR) and withdrawable (WMP) mounting options, allowing flexibility in switchgear installation and maintenance. The T designation typically indicates the inclusion of enhanced measurement, communication, or touch interface features on the trip unit. The NST suffix indicates compliance and classification related to the breaker version and frame style.
