Motor protection for the pit and the panel
The 3RA2125-4CA27-0AP6: This SIRIUS 3RA2 non-fused motor starter is a direct starter (non-reversing) with a bimetallic thermal overload relay built into the assembly — designed for the S0 feeder size. For a mine conveyor or mill feeder motor that sees frequent starts, that coordination matters. Mounting is snap-on to DIN rail or screw-mount with an additional push-in lug, and the unit is rated for vertical mounting only. The 45 mm width fits standard S0 panel layouts; with a depth of 97.1 mm and height of 193.1 mm, it leaves clearance for wiring and the supplied link module (3RA2921-1AA00) that connects the contactor and circuit-breaker section.
Power ratings and voltage coverage
Across the common industrial voltages, this starter delivers: 11 kW (15 hp) at 460/480 V, 21.9 A at 600 V, and 22 A at 480 V. It also covers 3 hp at 230 V, 5 hp at 200/208 V, 7.5 hp at 220/230 V, and 20 hp at 575/600 V — so it spans the 200–600 V range that covers most North American and European motor nameplates. The maximum rated operational voltage is 690 V, which gives headroom for 600 V class systems. The supplied contactor is a 3RT2027-1AP60, and the thermal overload release is electromechanical (bimetallic) — no electronic trip curve to set, just the dial on the front.
The 3RA2125-4CA27-0AP6 is part of the SIRIUS 3RA2 family, which is Siemens' compact motor starter platform for standard motor control centers and standalone panels. If you're maintaining a panel that was specified around a different SIRIUS variant, the mounting footprint and S0 sizing are consistent across the series — but the supplied contactor (3RT2027-1AP60) and link module (3RA2921-1AA00) are specific to this order code.
Clearance and environmental limits for installation
Clearance requirements around the unit: 30 mm upwards, 10 mm forwards, 10 mm downwards, 9 mm at the side, and 0 mm backwards (mounting surface). These are the minimum air gaps for heat dissipation from the bimetallic overload and the contactor coil — pack it tighter and you'll see nuisance trips on the thermal curve. Operating temperature range is -20 to +60 °C; storage range is -50 to +80 °C; transport range is -55 to +80 °C. Pollution degree 3 means it's rated for the conductive dust and humidity you'd find in a crusher house or mill building — not a clean room. The enclosure is not sealed (IP20 typical for SIRIUS contactor assemblies), so it lives inside a panel or MCC bucket.