What this enclosure base fits
The Siemens 3RW4776-0UB00 is the enclosure lower part (base) for the 3RW40 soft starter range, Size S12. It is the structural mounting chassis that houses the power stack and control board of the soft starter — not the complete unit itself. Size S12 is the largest frame in the 3RW40 family, designed for motor currents up to about 480 A depending on the specific soft starter variant. The base provides the mounting footprint and cable entry clearance for that power level.
Panel integration notes for the 3RW40 Size S12 base
As the enclosure lower part, this base determines the panel cutout and mounting hole pattern for the 3RW40 Size S12 soft starter. Verify the existing panel opening matches the Size S12 footprint before ordering — the base does not include the upper enclosure cover or the electronics module. The base provides the gland plate entry for motor and line power cables. For a 480 A class soft starter, expect cable sizes in the 185–300 mm² range; the base's cable entry clearance must accommodate those conductors with proper bending radius.