The 3RT2028-2BB44-3MA0: The S0 frame is the compact workhorse of the SIRIUS contactor family, sized for motor loads up to around 5.5 kW at 400 V AC-3. Spring-type terminals accept solid or stranded wire from 1 to 10 mm², or 2x 0.5 to 2.5 mm². This saves panel-build time versus screw terminals and holds well under vibration.
The 24 VDC coil pulls in at 80% of rated voltage (19.2 V) and drops out at 1.1× (26.4 V) — standard for industrial DC control circuits. The coil draw is 6 A at 24 V, 2 A at 48 V, and 0.3 A at 220 V, so the control transformer or power supply must be sized for the inrush. The main contactor is rated for motor duty at 5 hp at 230 V, which translates to roughly 5.5 kW at 400 V AC-3. Switching frequency limits: 1,000 cycles/hour at AC-1 (resistive), 750 at AC-2/AC-3 (motor start/run), and 250 at AC-4 (plugging/reversing). These are the maximum mechanical rates; thermal derating applies above 40 °C. Auxiliary contact block is built in: 1 NO + 1 NC, rated 6 A at 24 V, 3 A at 400 V. No separate auxiliary switch module is needed for basic feedback or interlocking. Arcing time is 10 ms at DC, fast enough for most PLC-driven sequences.
Dimensions: 102 mm high, 45 mm wide, 154 mm deep. The depth includes the coil terminals and auxiliary contacts; allow the full 154 mm behind the panel door. This covers most indoor industrial environments without derating.
For a BOM freeze or new design, the 3RT2028-2BB44-3MA0 is a stable choice. If you need a variant with screw terminals instead of spring-type, the 3RT2028-1BB44-3MA0 is the direct equivalent — same coil, same auxiliary contacts, same frame, same footprint. The only difference is the termination method.