Thermal Overload Relay, SIRIUS S3
The Siemens 3RU1146-4JB0-ZW98 is a SIRIUS thermal overload relay, Size S3, with CLASS 10 trip characteristics. Mounting is via contactor mounting (fastening method), with the relay designed to sit directly on a matching SIRIUS contactor. The relay carries ATEX protection type DMT 98 ATEX G 001, permitting use in potentially explosive atmospheres when paired with appropriate motor and installation. Front protection class is IP20, so the operator interface is touch-safe within the enclosure.
Key Ratings and Their Meaning
The relay's power dissipation is 5.7 W per pole, which must be accounted for in enclosure thermal calculations, particularly in a sealed panel with multiple relays. Short-circuit coordination is specified: with type of coordination 2, a gG fuse rated 125 A is required; with type of coordination 1, a gG fuse rated 200 A is required. This determines the upstream fuse selection for the motor branch circuit. The auxiliary contact ratings are given across multiple voltages: 1 A at 24 V, 3 A at 120 V, 2 A at 230 V, and 1 A at 400 V. These are the switching capacities for the built-in auxiliary contacts, used for signaling the overload condition to a PLC or motor starter. The relay is rated for 100 % relative humidity during operation, confirming suitability for high-humidity environments like washdown areas or outdoor cabinets.
Wiring and Integration
Main circuit terminals accept stranded conductors: 2x (10... 50 mm²) or single 10... 70 mm². For AWG: 2x (10... 1/0) or 1x (10... 2/0). Auxiliary and control circuit terminals accept solid conductors: 2x (0.5... 1.5 mm²) and 2x (0.75... 2.5 mm²); for AWG auxiliary: 2x (20... 16) and 2x (18... 14). All terminals are screw-type. Physical dimensions: width 70 mm, height 120 mm, depth 140 mm. This zero-clearance design allows the relay to be mounted flush against adjacent components, saving panel space. Shock resistance is rated at 8g for 10 ms, confirming the relay withstands vibration and shock typical in industrial environments with rotating machinery.