SIEMENS3UG4617-1CR20Digital 3-Phase Line Voltage Monitoring Relay, 160–690 V, Asymmetry and Auto Phase Sequence Correction, 2 CO, LCD

Product Description

What this part is

A Siemens SIRIUS 3UG4 digital monitoring relay for three-phase line voltage. It watches all three phases of a 160 to 690 V, 50/60 Hz supply and evaluates overvoltage, undervoltage, phase asymmetry, phase failure and phase sequence, driving two changeover contacts on a fault. An LCD on the front shows the measured value and the parameter being set, so thresholds are read as numbers rather than inferred from a scale marking. The relay is powered from the measured line itself.

Decoding the order code

3UG4 is the SIRIUS monitoring relay family, and the 6 that follows places it in the digital three-phase line-voltage group with LCD rather than the analogue potentiometer-set group. 17 is the specific function set, which in this position is the version with automatic phase sequence correction; the neighbouring 3UG4615 is the same measurement without that correction. 1C is the screw terminal connection method. R20 is the measuring range, 3 x 160 to 690 V AC.

What these specs mean in practice

Automatic phase sequence correction is the distinguishing feature and it changes what the relay is for. A conventional phase sequence relay trips when L1-L2-L3 arrive in the wrong order, which is what protects a pump or compressor from reverse rotation. This version instead accepts either sequence and adapts, so it is the correct choice on portable and hired equipment, generator-fed sites and machines that get moved between supplies, where a fixed-sequence relay would simply refuse to run after every reconnection. Asymmetry monitoring is adjustable from 0 to 20 percent and is what catches a soft-failing phase, a loose terminal or an unbalanced single-phase load before motor windings overheat. Hysteresis is settable from 1 to 20 V and the off delay from 0 to 20 s, which together stop the contacts chattering on a sagging or noisy supply.

Quantity and configuration

1 Pc. Monitoring relay only. No DIN rail, no terminal covers, no current transformers and no external reset pushbutton.

Installation and setup notes

The device is a 22.5 mm wide DIN rail unit, approximately 86 x 22.5 x 110 mm overall, with screw terminals. The three line conductors land directly on the measuring inputs and no separate control supply is required, since the relay derives its own power from the monitored voltage. Setting is done through the front buttons and read on the LCD; the two changeover contacts are taken to the contactor coil and to signalling. The unit is RoHS compliant.

Interchange guidance

The 3UG4615-1CR20 is the same measuring range and the same terminal arrangement without automatic phase sequence correction, which makes it a related device rather than a substitute where sequence independence is required — and the correct choice where reverse rotation must trip. Variants ending R21 or other R-codes cover different measuring ranges. The 3RR2 series measures current, not voltage, and mounts on a contactor rather than on rail.