What It Is and What It Does
The Siemens 3RT1025-1BM40 is a SIRIUS power contactor in size S0, designed for switching motor loads in industrial control panels. It mounts via screw and snap-on onto a 35 mm standard mounting rail per DIN EN 50022, so it integrates directly into a standard DIN-rail enclosure alongside other SIRIUS components. Its headline motor rating is 7.5 kW at 400 V in AC-3 duty — the standard category for starting squirrel-cage motors and disconnecting them under running conditions. That means it handles the inrush and breaking current of a motor up to that power without welding contacts or excessive wear. For more severe switching (AC-4, plugging or inching), it carries a 15.5 A rating at 400 V.
Key Ratings and What They Mean for Fit
The contactor is rated for a pollution degree of 3, which covers the industrial environment where conductive dust or condensation can occur — no need for an additional enclosure in most panel applications. The front face carries IP20 finger protection, so accidental contact during maintenance is prevented as long as the panel door is closed. For short-circuit coordination, the manufacturer specifies a gL/gG fuse of 25 A for type 2 coordination (no damage to the contactor) and 63 A for type 1 (the contactor may need replacement after a fault). This matters when designing the upstream protection — you size the fuse to clear a fault before the contactor welds shut. The coil is DC-operated with a closing and holding power of 5.4 W. That is a continuous-duty coil, so it stays energized without overheating — typical for applications where the contactor is held in for long periods. Operating temperature range is -25 to +60 °C, which covers most indoor industrial environments. The contactor's mechanical life is rated at 10 million operations typical, so it is built for high-cycle applications like conveyor lines or pump stations.
Integration Notes
Width is 45 mm, side clearance 6 mm. Depth 101 mm, height 85 mm. The auxiliary contacts are rated for switching at various control voltages: 10 A at 24 V, 2 A at 60 V, 1 A at 110 V, and 0.3 A at 220 V. These ratings are for the auxiliary contact block, so if you are switching a PLC output or a relay coil, stay within these limits per the voltage you are using.