The Siemens 3RB2015-1RB0 is a SIRIUS solid-state overload relay for three-phase motor circuits.
The operating voltage is rated up to 690 V AC-3 (with degree of pollution 3), so it can be used in 400 V and 690 V line supplies — common in European and North American industrial panels. The auxiliary contact block provides 1 NO + 1 NC contact, enough to signal a trip to a PLC or drop out a holding circuit.
The relay is designed for contactor mounting — it clips onto a SIRIUS S00 contactor without additional wiring between the overload and contactor power terminals. Dimensions are 73 mm deep, 45 mm wide, 64 mm high, and it fits any mounting position. Clearance of 6 mm is required at the side for heat dissipation; zero clearance is needed upwards, forwards, or backwards. That is a tight footprint for a motor starter assembly.
This part carries ATEX approval (PTB 06 ATEX 3001 Ex II (2) GD) for use in potentially explosive atmospheres — specifically for motors in gas and dust zones where the overload relay sits outside the hazardous area but protects motors inside it. It withstands 100% relative humidity during operation, so condensation in a non-conditioned panel is not a problem. Surge voltage resistance is 6 kV, and ESD immunity meets IEC 61000-4-2 (6 kV contact / 8 kV air discharge).