The Siemens 3RB2016-1ND0 is a SIRIUS solid-state overload relay for three-phase motor protection, rated CLASS 10E trip class. It mounts directly onto a contactor (contactor mounting).
Three poles for the main current circuit, so it covers a standard three-phase motor. The auxiliary circuit has one normally-closed contact — that's your trip alarm or feedback to the PLC. The ATEX approval (PTB 06 ATEX 3001 Ex II (2) GD) means it's certified for use in potentially explosive gas and dust atmospheres — the (2) indicates it's associated apparatus that can be installed in the safe area but protects the motor in the hazardous zone. That's a big deal for chemical, grain, or paint-line applications where a standard thermal overload won't fly. Solid-state construction means no bimetallic strip to drift with age or ambient temperature swings. The relay measures true motor current via internal CTs and applies an I²t curve. It's also shock-rated to 15g / 11 ms and operates in 100 % relative humidity, so it's fine in washdown areas or on vibrating machinery — just keep the ambient between -25 °C and +60 °C during operation.
The relay is 45 mm wide, 64 mm tall, and 73 mm deep. Mounting position is any, so you can lay it sideways in a shallow enclosure if needed.