What it is and what it does
The Siemens 3RT2645-1AF03 is a SIRIUS S3-size capacitor contactor designed for switching capacitor banks in power factor correction (PFC) applications. It switches capacitive loads without the inrush surge welding the main contacts — that's the difference from a standard motor contactor. The 110 V AC 50 Hz coil is screw-type terminated. Rated for 6 A at 230 V and 3 A at 400 V, this contactor handles the steady-state current of a capacitor bank at those line voltages. At 690 V the rating drops to 0 A — it's not intended for 690 V bank switching. The switching frequency is 200 operations per hour at 230/240 V, dropping to 40 per hour at 600/690 V, so it's built for periodic compensation, not continuous hunting. An auxiliary contact block can be attached (1 available slot), and the contactor includes one instantaneous contact for feedback or interlocking.
Mounting and integration
Mounts via screw or snap-on onto 35 mm DIN rail per EN 50022. The mounting position is flexible: +/-180° rotation on a vertical surface, plus +/-22.5° tilt forward/backward — useful when the panel layout forces an odd angle. Dimensions are 80 mm wide, 140 mm high, 152 mm deep — an S3 frame that fits alongside other SIRIUS gear on the same rail. Power wiring accepts stranded conductors up to 70 mm² (2x or 1x) and solid conductors from 0.5 to 4 mm². The coil terminals are screw-type, same as the main terminals — no push-in or spring-cage on the coil, so keep a screwdriver handy. Operating temperature range is -25 to +60 °C; storage range -55 to +80 °C. The arcing time is 10 to 20 ms, and the dropout time at AC is 10 to 21 ms.