Capacitor switching contactor, AC-6b rated 75 kVAr at 400 V
The Siemens 3RT2637-1AV05 is a 3-pole capacitor contactor from the SIRIUS series, size S2, designed specifically for switching capacitor banks in power factor correction (PFC) systems. Its AC-6b duty rating of 75 kVAr at 400 V AC, 50 Hz means it handles the inrush current peaks typical when energizing a capacitor bank — up to 100× the rated current for a few milliseconds — without welding the main contacts. The built-in 2 NC auxiliary contacts (screw terminal) can be wired into the controller logic to confirm the contactor state or interlock with the main breaker.
The screw terminals accept 0.5–16 mm² conductors (solid or ferruled stranded). The 400 V AC coil is 50 Hz only — verify supply frequency before wiring; a 60 Hz coil variant would carry a different order code. The capacitor bank connects to the main poles; the NC aux contacts are available on terminals 21-22 and 31-32.