Capacitor switching contactor for power factor correction banks
The Siemens 3RT2625-1AC25 is a SIRIUS capacitor contactor, size S0, designed specifically for switching capacitor banks in power factor correction (PFC) applications. Unlike a standard motor contactor, it includes pre-charge resistors to limit inrush current when energising the capacitor, preventing contact welding and nuisance fuse blows. This frequency ceiling is the practical limit for capacitor bank cycling in PFC controllers.
Panel fit and termination details
The S0 frame size is a common footprint across the SIRIUS 3RT2 range, so panel cut-outs and busbar layouts for the S0 family transfer directly. Screw-type terminals on both the main poles and the coil. The terminal capacity covers the typical power and control wiring for capacitor banks up to the contactor's rating. This eases integration into tight panels where the contactor must be oriented to match the capacitor bank layout.
Environmental limits and switching performance
The arcing time is 4…16 ms at AC, with a typical value of 10 ms. These arcing times are consistent with the pre-charge resistor design that limits the capacitor inrush to a level the main contacts can handle without excessive wear.