The ABB 5S4000 R4000 AR1/LI WMP 3P NST is a low‑voltage air circuit breaker (ACB) designed for heavy‑duty electrical distribution and protection in industrial and commercial power systems. It belongs to ABB’s 5S series, supporting a continuous rated current of 4000 A in a three‑pole (3P) configuration. The breaker is built with a withdrawable moving part (WMP) format, enabling easy insertion and removal from compatible switchgear frames for maintenance and operation.