The Siemens 3RB2015-1NB0 is a SIRIUS solid-state overload relay — no bimetals to drift, no heater packs to swap. It protects motors against overload and phase loss by monitoring current through the main circuit and tripping when the thermal model hits the Class 10E curve. That matters when you're paying your own electric bill and can't afford a false shutdown on a conveyor.
This relay mounts directly onto a contactor — no DIN rail needed. The 45 mm width and 64 mm height keep it compact inside a panel, and the 73 mm depth means it won't crowd the gland plate. It can sit in any orientation, which helps when you're squeezing it into a tight enclosure. The ATEX Ex II (2) GD approval (PTB 06 ATEX 3001) means it's allowed in Zone 2 gas and Zone 22 dust areas when installed per the certificate. That's a real differentiator for grain elevators, paint booths, or chemical mixing lines.
Switching and wiring
The auxiliary contacts handle a range of control voltages: 2 A at 24 V, 4 A at 120 V, 3 A at 230 V, and 0.55 A at 60 V, among others. That covers most PLC output cards and control transformers without needing an interposing relay. Main circuit terminals accept solid wire from 0.5 to 4 mm², or two conductors up to 2.5 mm² each. The screw-type terminals are standard for panel wiring — no special tooling needed. Auxiliary and control circuits also use screw terminals.