Siemens 3UG4618 2CR20 Phase Sequence Undervoltage Relay Module

Siemens 3UG4618-2CR20 SIRIUS Phase Sequence Undervoltage Relay Module is a DIN-rail mounted digital monitoring relay for three-phase voltage with a neutral conductor, designed to ensure correct phase sequence and guard against phase failures and undervoltage/overvoltage conditions while automatically correcting phase order. It uses two changeover contacts (2 CO): one output for automatic phase correction and one for signaling power system faults, enabling integrated protection actions in motor and drive circuits. The device monitors 3-phase voltages in the 90–400 V AC range at 50–60 Hz, with a voltage hysteresis of 1–20 V, an OFF delay of 0–20 s, and an asymmetry tolerance of 0–20%. An on-board LCD readout provides status information, and wiring is via a spring-loaded connection system for secure, tool-free termination. The unit carries IP20 protection and is intended for panel mounting in industrial control panels as part of Siemens SIRIUS line monitoring relays, offering coordinated protection without altering the main power contacts.