Square D LKX36400 S3B Electronic Trip Circuit Breaker

Square D LKX36400 S3B Micrologic 400A Electronic Trip Circuit Breaker is a 400-amp electronic-trip molded‑case breaker designed for 240–600 VAC service in commercial and industrial electrical distribution. Equipped with the Micrologic S3B trip unit, this device provides Long-Time, Short-Time and Instantaneous protection (LSI) to help coordinate upstream and downstream protective devices while delivering reliable overcurrent shutdown on fault conditions. It is intended for use in panels and feeders that power equipment and circuits in harsh or high‑demand environments, where fast, accurate tripping and solid-state protection are essential. With a 240–600 VAC rating and a 400 A current rating, the LKX36400 S3B is suited for protecting feeders, distribution circuits, and industrial machinery, offering integrated electronic protection without the need for external CTs or mechanical trip adjustments.