The Siemens 3RB2015-1SB0 is a SIRIUS solid-state overload relay — a Class 10E device that protects three-phase motor circuits against overcurrent and phase failure without the mechanical wear of a bimetallic strip. It mounts directly onto a SIRIUS S00 contactor (contactor mounting, not DIN rail), saving panel space and simplifying the wiring between the contactor and the overload block. Rated for a maximum operating voltage of 690 V AC-3 and with a surge voltage resistance of 6 kV, it handles standard 400 V and 480 V motor feeds with headroom. The relay provides one normally-open and one normally-closed auxiliary contact for status feedback or trip signalling back to the PLC.
The switching current capability varies with the control voltage: 2 A at 24 V, 4 A at 120 V, 3 A at 230 V, and 0.55 A at 60 V, among other points. These are the make/break ratings for the auxiliary contacts — useful when selecting the PLC input or relay coil the overload relay will drive directly. With IP20 protection on the front and screw-type terminals for both main and control circuits, it is suited for installation inside a standard IP54 or higher enclosure. The ATEX approval (PTB 06 ATEX 3001 Ex II (2) GD) means it can be used in Zone 2 gas or Zone 22 dust areas when paired with an appropriate upstream protection device.
This overload relay is designed for three-phase motor protection in industrial control panels — conveyors, pumps, compressors, fans, and machine tools. The SIRIUS S00 contactor frame size (the relay mates with contactors like 3RT7014 or 3RT7016) keeps the motor starter compact, typically occupying a 45 mm wide footprint on the panel subplate.