The Siemens 3RB2015-2NB0 is a SIRIUS solid-state overload relay — the part that sits between a contactor and a motor, watching current and tripping on overload before the winding cooks.
Mounts directly onto a contactor — no DIN rail needed, which saves a slot in a crowded panel. Accepts solid or stranded wire from 0.5 to 4 mm² (or 2× 0.5 to 2.5 mm²), with AWG equivalents of 2× 18 to 14 for the main contacts. That's a tight fit for retrofit into existing panels without re-spacing rails.
IP20 on the front — finger-safe for the panel builder, but not for washdown; keep it inside the enclosure. ATEX certified PTB 06 ATEX 3001 Ex II (2) GD, so it's approved for use in potentially explosive atmospheres where a motor overload could ignite a gas or dust cloud. The relay itself is not in the hazardous zone — it sits in the safe-area panel, protecting the motor in the zone. Shock-rated to 15g for 11 ms, which covers most industrial vibration from nearby crushers or presses. Storage and transport range is -40 to +80 °C, wider than the operating range — fine for warehouse or trucking in extreme climates.