Carlo Gavazzi SY4H-175 Electromechanical Relay

The SY4H-175 is an electromechanical phase-monitoring relay from Carlo Gavazzi designed to protect three‑phase loads by watching for phase faults and imbalances. It provides a single SPDT output rated at 10 A to switch a controlled load and is packaged as a plug‑in module in Gavazzi’s S‑housing with LED indicators for both the power supply and the output state. The device monitors phase sequence, phase loss, phase asymmetry, and phase angle on a 3‑phase network, and can measure asymmetry on 3‑phase voltage without neutral, delivering early warning of abnormal power quality to drive protective actions. A built‑in timer function is adjustable to delay actions as needed, and the asymmetry sensitivity is knob‑selectable to match system tolerances. The SY4H‑175 is designed for panel insertion using compatible Gavazzi sockets and is commonly used to protect motors, heaters, and pumps in HVAC, process lines, and general industrial automation where monitoring mains quality and load balance helps prevent downtime.