Coupling contactor for signal isolation
The Siemens SIRIUS 3RT2027-2KG40 is a size S0 coupling contactor — a magnetically latched relay designed to isolate control signals from power circuits, typically used between a PLC output and a motor starter or contactor coil. It carries a 24 V DC coil rated at 10 A, meaning it can switch a substantial inductive load on the control side without overloading the PLC card. Spring-type terminals (cage clamp) accept solid or stranded wire from 1 to 10 mm², and dual-wire entry handles 2x (0.5 to 2.5 mm²) for daisy-chaining. No auxiliary switch is built in — plan for an external auxiliary contact block if feedback is needed.
Switching capacity across voltages
Rated for resistive and motor loads across common control voltages: 48 V at 2 A, 60 V at 2 A, 110 V at 1 A, 125 V at 0.9 A, 220 V at 0.3 A, and 400 V at 3 A. At 230 V it carries a 5 hp motor load — a common rating for small pump or fan starters. The DC operate time is 19 to 21 ms with an arcing time of 10 ms, giving predictable timing for sequence interlocking.
Mechanical and thermal limits
Mechanical life is 10 million operations typical. Maximum switching frequency depends on duty: 1000 cycles/hour for AC-1 (resistive), 750 for AC-2 and AC-3 (motor starting/running), 250 for AC-4 (plugging/inching). Operating temperature range is -25 to +60 °C, storage -55 to +80 °C. Mounting position is flexible — +/-180° rotation on a vertical surface, and can be tilted forward/backward by +/-22.5°.
DIN rail integration and clearances
Mounts via screw and snap-on onto 35 mm DIN rail per DIN EN 60715. Dimensions: 45 mm wide, 102 mm high, 107 mm deep — fits a standard S0 footprint. Required clearances: 10 mm upwards, 10 mm forwards, 10 mm downwards, 6 mm at the side. Main contacts are 18 to 8 AWG rated. The spring terminals reduce wiring time and resist vibration loosening in transport or high-vibration panels.