What it is and what it does
The Siemens 3RT2646-1AP03 is a SIRIUS capacitor contactor, size S3, designed for switching capacitive loads — typically power-factor-correction capacitor banks in industrial and commercial distribution panels. Rated for AC coil voltage at 230 V, 50 Hz, it switches 6 A at 230 V, 3 A at 400 V, and 0 A at 690 V — meaning it is sized for low-voltage capacitor banks, not 690 V applications. Mounts via screw and snap-on onto 35 mm DIN rail per DIN EN 50022, with a ±180° rotation possible on a vertical surface and ±22.5° tilt forward/backward — useful when panel layout forces an unconventional orientation.
Key ratings and what they mean for fit
The switching current ratings are given per voltage: 6 A at 24 V, 6 A at 230 V, 2 A at 60 V, 1 A at 110 V, 0.9 A at 125 V, 0.3 A at 220 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. Maximum switching frequency varies by voltage: 150 operations/hour at 230/240 V, 80 at 400 V, 53 at 480/500 V, 32 at 600 V, and 30 at 690 V — so for high-cycle capacitor banks (e.g., frequent power-factor correction), keep the bank voltage at or below 240 V to reach 150 ops/h. Operating temperature range -25 to +60 °C, storage -55 to +80 °C — the storage limit governs handling and shipping, not running conditions.
Wiring and integration
Solid wire capacity: 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), 2x 4 mm². Stranded: 2x (10 to 70 mm²) or 1x (10 to 70 mm²). The main power terminals accept up to 70 mm² stranded — typical for a 50–70 A capacitor bank feed. Dimensions: 152 mm depth, 80 mm width, 140 mm height. The 80 mm width is the DIN-rail footprint — plan for 80 mm per unit in the enclosure layout. Coil terminals are screw-type; arcing time is 10 to 20 ms at AC, with a dropout time of 10 to 21 ms at AC — fast enough for most capacitor switching sequences.