SIRIUS S3 power contactor — 66 A AC-4, screw terminals, current production
The Siemens 3RT1045-1AP04-3MA0 is a SIRIUS power contactor in frame size S3, designed for switching motor loads and resistive loads in industrial control panels. It carries a 66 A rated operational current at AC-4 / 400 V, which is the severe-duty category for plugging and inching — frequent make-and-break of stalled or reversing motors. That rating is the one that governs real-world reversing or jogging duty, not the higher AC-3 figure. The contactor mounts via screw and snap-on onto 35 mm or 75 mm standard DIN rails, fitting into a 70 mm wide enclosure slot. The front face carries an IP20 rating with a cover or box terminal; the terminal area itself is IP00, meaning the wiring compartment expects enclosure protection.
Ratings that decide the fit
At AC-2 duty (slip-ring motors, starting only) the contactor is rated 37 kW at 400 V. At AC-4 — the category that matters for reversing, inching, and plugging — it delivers 66 A at 400 V. For direct-on-line starting (AC-3), the motor ratings are 45 kW at 500 V and 21.1 kW at 690 V. The 500 V figure is the higher power point; the 690 V figure reflects the voltage derate typical of this frame. Mechanical life is listed at 10 million operations typical. Maximum switching rates vary by duty: 1 000 cycles/hour at AC-3, 900 at AC-1, 400 at AC-2, and 300 at AC-4. The AC-4 rate is the limiting one for high-duty-cycle reversing applications.
Termination and wiring
Main current circuit connections use screw-type terminals. The main circuit accepts stranded conductors from 2x 10 mm² up to 2x 50 mm². The auxiliary/control circuit accepts solid conductors: 2x (0.5... 1.5 mm²), 2x (0.75... 2.5 mm²), or max 2x (0.75... 4 mm²). The control coil operates at 50 Hz, with a rated control supply voltage of 230 V at that frequency. Side-by-side mounting is permitted, which means multiple contactors can be ganged on the same DIN rail without derating for heat buildup in still air — though the operating temperature range of -25 to +60 °C should be respected for the aggregate load.
Lifecycle and compliance
The 3RT1045-1AP04-3MA0 is sourced to order against an RFQ through independent distribution channels. Availability and current pricing are confirmed at quote time. For a BOM-line commitment, the AC-4 current rating and frame size are the fit-critical parameters that confirm this contactor matches the original specification.