What this part is and what it does
The Siemens SIRIUS 3RT2517-2BB48-0PT1-ZX95 is a pole-changing contactor — a specialized variant of the standard SIRIUS contactor family, designed for switching pole-changeable motors (e.g., Dahlander or separate-winding two-speed motors) where the winding configuration must be reconfigured between low and high speed. It is rated for AC-3 duty at 5.5 kW at 400 V, with a 24 V DC coil, and comes in size S00 with spring-loaded terminals. The order code includes two factory-fitted 3RH2911-2DA20 auxiliary contact blocks, each providing 2NO+2NC contacts, mounted left and right. The part ships in reusable packaging of 80 pieces.
Key ratings and what they mean for fit
The AC-3 rating of 5.5 kW at 400 V is the motor-switching capability — this is the rating that governs the contactor's ability to make and break a squirrel-cage motor under starting and running conditions. For a pole-changing contactor, this rating applies to each winding configuration; the contactor must handle the inrush and the switched current for both speed settings. The 24 V DC coil is a low-voltage control standard in many industrial panels, but note that DC coils draw continuous holding current — unlike AC coils that have a reduced holding power — so the control transformer or power supply must be sized for the steady-state draw. The size S00 footprint (45 mm width) snaps onto a 35 mm DIN rail per EN 50022, and the spring-loaded terminals accept solid or stranded conductors without needing a screwdriver for the main circuit — a time-saver during panel wiring.
Deployment context
This contactor snaps onto a 35 mm DIN rail per EN 50022, making it straightforward to integrate into a standard control panel enclosure. The spring-loaded terminals reduce wiring time compared to screw terminals, especially in high-density panels where access is tight. The pole-changing function is typically used in applications like fans, pumps, or machine spindles that require two discrete operating speeds — the contactor switches the motor winding configuration, not just the power supply.