Motor starter assembly — what ships and what it covers
The 3RA2125-4ED27-0BB4 is a SIRIUS non-fused motor starter, size S0, combining a contactor and overload relay in one direct-starter package. It ships with the 3RT2027-1BB40 contactor, the 3RA2921-1BA00 link module, and the 8US1251-5NT10 busbar adapter — the BOM line is a complete feeder, not a loose contactor. The 24 V coil (50/60 Hz) pulls from a standard control transformer.
Overload and short-circuit protection — Class 10 trip curve
The magnetic short-circuit trip handles the instantaneous fault clearing. Pollution degree 3 (conductive pollution or dry non-conductive pollution that becomes conductive due to condensation) is the design environment — this starter is rated for industrial control panels where the atmosphere is not climate-controlled.
Panel fit and mounting — vertical snap-on, 60 mm busbar
Mounting is vertical only, snapping onto 60 mm busbar systems via the included adapter. The footprint is 45 mm wide × 260 mm high × 165 mm deep — the S0 frame size keeps the width to a single 45 mm module, so it fits standard 600 mm wide enclosures with room for gland plates and wiring ducts. Clearance requirements: 30 mm upwards, 10 mm forwards, 10 mm downwards, 9 mm at the side, and 0 mm backwards — the back face sits flush against the mounting surface. No rear gap means the busbar adapter must be seated before the starter is snapped on.
The supplied sub-components (contactor 3RT2027-1BB40, link module 3RA2921-1BA00, busbar adapter 8US1251-5NT10) are each individually orderable as spares, but the 3RA2125-4ED27-0BB4 assembly is the single BOM line for a complete feeder — no separate sourcing of contactor and overload relay.