What this part is and what it does
The Siemens 3RT1045-1AL28-0PA4 is a 3-pole power contactor from the SIRIUS 3RT1 series, rated for AC-3 duty at 80 A and 37 kW at 400 V. The 230 V AC coil operates at 50/60 Hz. The AC-3 rating is the motor-switching curve — this contactor is sized for starting and stopping squirrel-cage induction motors under full load, not for resistive heating or DC loads. The Size S3 frame carries screw terminals and includes one normally-open and one normally-closed auxiliary contact mounted on the lateral right side.
Integration notes
The Size S3 footprint mounts on standard DIN rail in a control panel. The 230 V AC coil draws its control voltage from the panel's line side — verify the control transformer rating if multiple contactors share the same circuit. The auxiliary contact block (1 NO + 1 NC) is factory-fitted on the lateral right; no additional side-mounting hardware is needed for basic feedback or interlock wiring. Screw terminals accept up to the wire gauge specified for 80 A motor branch circuits.