SIRIUS 3RT2645-1AF05 capacitor contactor — 400 V 3 A, Size S3
The Siemens 3RT2645-1AF05 is a SIRIUS capacitor contactor, Size S3, designed for switching capacitor banks in power-factor correction panels. Its 400 V 3 A rating covers the typical load profile of a capacitor bank at that voltage — the inrush current from charging capacitors is what this contactor is built to handle, not a resistive or motor load. The coil is AC-operated with screw-type terminals.
Mounting and integration
Mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 50022. The 80 mm width and 140 mm height with 152 mm depth fit a standard S3 contactor footprint — panel cutouts and gland plates sized for S3 will accept this unit without rework. The mounting position allows ±180° rotation on a vertical surface and ±22.5° tilt forward/backward, which helps when the DIN rail is crowded.
Wiring and termination
Power terminals accept solid conductors: 2x (0.5…1.5 mm²), 2x (0.75…2.5 mm²), or 2x 4 mm². For stranded wire, the range goes up to 2x (10…70 mm²) or 1x (10…70 mm²). The auxiliary contact block is attachable — one slot available for adding a mirror contact or signalling contact. Coil terminals are screw-type.
Switching ratings and operating limits
Rated for AC switching at 50 Hz. The contactor breaks 6 A at 24 V, 6 A at 230 V, 3 A at 400 V, and 0 A at 690 V — the 690 V entry confirms this contactor is not intended for 690 V capacitor switching. Mechanical operating frequency tops out at 200 cycles per hour at 230/240 V, dropping to 40 cycles per hour at 600/690 V. Arcing time is 10…20 ms, with a spread of 10…21 ms at AC. Ambient operating range is -25…+60 °C; storage range -55…+80 °C.