S0 reversing starter, 25 A AC-3, busbar snap-on
The 3RA2220-4DH27-0BB4: The Class 10 trip characteristic means it clears overloads fast enough to protect standard squirrel-cage motors on start-up without nuisance tripping on a normal acceleration curve.
Mounting and wiring — 60 mm busbar, spring terminals
This unit snaps directly onto 60 mm busbar systems — no DIN rail adapter needed, no extra bracketry. The vertical mounting position is mandatory per the spec; horizontal mounting would compromise the thermal calibration of the overload relay. Main circuit connections are spring-loaded terminals — push the stripped wire in, no screwdriver torque to check. The S0 frame keeps the width at 90 mm and depth at 165 mm, which fits a standard 260 mm tall enclosure section without crowding the gland plate.
What's in the box — contactor and link module included
The reversing starter ships as a pre-assembled unit containing a 3RT2027-2BB40 contactor and a 3RA2921-2AA00 link module. The contactor is the switching element; the link module provides the mechanical and electrical interlock between the forward and reverse contactors, preventing both from closing simultaneously.
Clearance and ambient limits
Minimum clearances: 50 mm upward, 32 mm forward, 10 mm to the side and downward — zero clearance needed behind the unit. Ambient operating range is -20 to +60 °C with the same range for temperature compensation; storage and transport tolerance extends from -50 to +80 °C.