Siemens 3UG3511-1BQ50 Monitoring Relay

Siemens 3UG3511-1BQ50 Monitoring Relay is a compact 22.5 mm-wide device designed for phase sequence and phase-loss monitoring on three-phase AC power systems. It accepts a three-phase supply in the range of 3 × 200 to 3 × 460 V AC at 50/60 Hz and uses screw-terminal connections for secure, vibration‑resistant wiring. The relay provides a single changeover contact to signal fault conditions, enabling straightforward integration with PLCs, motor starters, and control circuits. This model is intended for panel-mounted control applications where maintaining correct phase sequence and voltage presence is critical to prevent motor damage, abnormal startup, or bearing wear caused by phase loss or reversal. It is part of Siemens’ 3UG3511 analog monitoring relay family, a line of compact phase‑monitoring modules commonly used in industrial automation to verify the health of three‑phase supplies before energizing equipment. The -BQ50 variant is referenced in catalogs as a phase-sequence/voltage‑loss monitor with a signaling changeover contact, and it is designed to fit standard 22.5 mm mounting spaces in control panels.