What it is and what it handles
The Siemens 3RT1045-1CP04-0KV0 is a SIRIUS power contactor in the S3 frame size, built for switching motor loads in industrial control panels. Its headline rating is 45 kW at 500 V under AC-3 duty — that's the standard motor-switching category per IEC 60947-4-1, so it directly drives a 45 kW induction motor on a 500 V line without derating. At 400 V AC-4, the rating is 66 A, which covers reversing or inching applications where the contactor makes and breaks stalled-rotor current. The AC-2 rating at 400 V is 37 kW, suited for wound-rotor motors or slip-ring loads. The coil operates on 50 Hz at 230 V rated value, with a pickup range of 0.8 to 1.1 times rated voltage — meaning it pulls in reliably even if the line dips to 184 V. The contactor mounts via screw or snap-on onto 35 mm or 75 mm standard DIN rail, and side-by-side mounting is permitted, which saves panel width when stacking multiple contactors in a motor control center.
Mounting and termination
The S3 frame measures 146 mm high, 70 mm wide, and 201 mm deep — check your enclosure depth before committing the BOM line. Main circuit terminals are screw-type, accepting 2x (10 to 50 mm²) stranded or 2x (2.5 to 16 mm²) solid/stranded. Auxiliary terminals handle 2x (0.5 to 1.5 mm²) solid or 2x (0.75 to 2.5 mm²) stranded, up to 4 mm² max. The front face carries IP20 protection with the cover or box terminal fitted; the terminal area itself is IP00, so keep live parts guarded inside the panel.
Environmental and mechanical endurance
Operating temperature range is -25 to +60 °C, storage from -55 to +80 °C. Pollution degree 3 means it tolerates conductive dust or condensation typical of factory-floor panels. Mechanical life is 10 million operations typical. Maximum switching rates are 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 lower because each cycle stresses the contacts harder. Shock resistance is 10.6 g for 5 ms AC and 6.2 g for 10 ms AC; DC dropout time is 14 to 20 ms, arcing time 10 to 15 ms.