What this part is and what it does
The Siemens SIRIUS 3RT2645-1AP03 is a capacitor contactor in the size S3 frame, designed specifically for switching capacitor banks in power factor correction (PFC) applications. It is rated for 230 V at 50 Hz, the standard line voltage and frequency for many European and Asian industrial panels. Unlike a standard motor contactor, a capacitor contactor must handle the high inrush current and transient stress when a discharged capacitor bank is switched onto the line. The 3RT2645-1AP03 is built for that duty cycle, with an arcing time of 10 to 20 ms and a switching frequency of up to 200 operations per hour at 230 V to 240 V, tapering to 40 operations per hour at 690 V.
Mounting and integration into the panel
Mounts via screw and snap-on onto 35 mm DIN rail per DIN EN 50022. The mounting position allows +/-180° rotation on a vertical surface and can be tilted forward and backward by +/-22.5° on a vertical mounting surface, giving flexibility in tight enclosures. Dimensions are 80 mm wide, 140 mm high, and 152 mm deep — the depth is the dimension that projects from the DIN rail, so verify clearance to the enclosure door or rear panel. The magnet coil termination uses screw-type terminals. Power-side conductor cross-sections are rated for solid: 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), 2x 4 mm²; and stranded: 2x (10 to 70 mm²), 1x (10 to 70 mm²). At 40 °C ambient, a single 50 mm² conductor is permitted; at 60 °C, two 35 mm² conductors.
Switching ratings and thermal limits
Switching current is rated per voltage: 6 A at 24 V AC, 6 A at 230 V AC, 3 A at 400 V AC, and 0 A at 690 V AC. The contactor also carries a 1 A rating at 110 V AC and 0.9 A at 125 V AC. Operating temperature range is -25 to +60 °C during operation, with storage from -55 to +80 °C. The instantaneous contact is rated for 1 make operation, consistent with capacitor switching where the contact closes once per switching cycle. The operating frequency at 230 V maximum is 200 operations per hour, which is adequate for automatic PFC controllers switching at intervals of several minutes.
Lifecycle and sourcing posture
For BOM freeze or new design-ins, this part is a standard catalog item from the SIRIUS family. Sourcing is straightforward — quoted to order against an RFQ through normal Siemens distribution.