What it is and what it does
This Siemens SIRIUS 3RT1024-3EG28-0MA3 is a Size S0 power contactor built for switching three-phase motor loads in industrial control panels. It carries a 7.5 kW rating at both 500 V and 690 V in AC-3 duty, which is the standard category for starting and disconnecting squirrel-cage induction motors on the fly. That 7.5 kW figure tells you it's sized for a 10 HP motor on a 480 V line or roughly a 10 kW motor on a 690 V supply — a common sweet spot for pumps, fans, and small conveyors.
Key ratings and what they mean for fit
The AC-3 rating is the one that governs motor switching: 7.5 kW at 690 V and the same at 500 V. That means this contactor will handle a 10 HP, 480 V three-phase motor without derating. The AC-2 rating at 400 V is 5.5 kW — that's for slip-ring motors where the starting current is lower but the switching frequency can be higher. The AC-4 rating at 400 V is 12.5 A, which covers reversing or inching duty where the contactor makes and breaks the full locked-rotor current. It has two instantaneous auxiliary contacts rated at 10 A at 24 V and 6 A at 230 V. That's enough for a feedback signal to a PLC or a holding circuit for a start/stop station. The auxiliary contacts are built into the front, not add-on blocks, which saves a DIN slot. Operating temperature range is -25 to +60 °C, which covers most indoor panel environments. Pollution degree 3 means it's rated for industrial atmospheres where conductive dust or condensation can occur — typical for a non-sealed panel on a factory floor. The IP20 front protection means it's finger-safe from the front but not splash-proof; it needs to live inside an enclosure.
Mounting and wiring
Mounts on a 35 mm DIN rail per EN 50022, either snapped on or screwed. The S0 frame is 45 mm wide, 88 mm tall, and 140 mm deep — that's a standard footprint that fits most panel layouts without surprises. The main circuit uses screw-type terminals, which take 2x (0.25 to 2.5 mm²) solid or 2x (1 to 2.5 mm²) stranded, and can handle up to 2x 10 mm². That's a solid grip for motor leads up to about 8 AWG. The auxiliary terminals take 2x (0.25 to 2.5 mm²) solid. The integrated RC surge suppressor across the coil means you don't need an external snubber for inductive load switching. That cleans up the panel layout and saves a terminal block. Side-by-side mounting is allowed, so you can gang multiple contactors on the same rail without derating, as long as you respect the 6 mm side clearance for heat dissipation.