The Siemens 3RT2637-1AV03 is a capacitor contactor from the SIRIUS series, rated AC-6b 75 kVAr at 400 V for switching capacitive loads. The 3-pole configuration with a 400 V AC 50 Hz coil and screw terminals fits standard panel layouts. Size S2 frame keeps the DIN-rail footprint compact for power-factor correction banks.
What the AC-6b rating means for fit
AC-6b is the IEC utilization category for switching capacitor banks. The 75 kVAr at 400 V rating governs the maximum reactive power this contactor can make and break without welding or excessive wear. That figure assumes a 50 Hz supply; the inrush current from discharged capacitors is typically 20–30× rated current, so the contactor's design margin in AC-6b is what protects the bank and the panel. A standard AC-3 motor-rated contactor of similar frame size would not survive repeated capacitor switching.
Panel integration notes
Size S2 mounts on 35 mm DIN rail per EN 60715. Screw terminals accept 1.5–6 mm² stranded or solid copper. The 400 V AC coil draws its rated VA at pickup and lower holding VA — verify the control transformer is sized for the inrush if multiple contactors pull in simultaneously. The auxiliary contacts are electrically isolated from the main poles, so feedback wiring to a PLC input is straightforward.