Motor switching and coil fit
The 3RT2028-1AU60 is a SIRIUS 3RT power contactor rated AC-3e/AC-3 at 38 A, delivering 18.5 kW at 400 V for three-phase induction motors. That AC-3e rating means it handles the high inrush of starting a squirrel-cage motor and then breaks the running current — the duty cycle that matters for conveyors, pumps, and compressors. The coil is 277 V AC at 60 Hz, so it's specced for North American control voltages on a 60 Hz supply; verify your control transformer matches before wiring. The built-in auxiliary contact block gives you 1 NO + 1 NC, enough for a basic seal-in circuit plus a status feedback to the PLC. For more aux contacts, the S0 frame accepts snap-on side-mount blocks without additional wiring space.
Size S0 frame — the compact footprint that fits standard DIN rail or panel-mount. Screw terminals accept up to the rated wire size for 38 A; torque them to the Siemens spec on the label. The 105 x 90 x 55 mm package leaves room for auxiliary blocks and a separate overload relay alongside it in the enclosure.