The Siemens 3RT1024-1AD20-ZW98 is a 3-pole contactor from the SIRIUS series, rated for AC-3 duty at 5.5 kW at 400 V, with a 42 V AC coil operating at 50/60 Hz. The AC-3 rating means it is sized for switching squirrel-cage motors — starting and stopping under load — up to that power level. The 42 V coil makes it a fit for control circuits running on a 42 V AC supply, common in older or safety-isolated panels. Size S0 and screw terminals keep it to a standard DIN-rail footprint, so it slots into existing panel layouts without re-drilling.
The 42 V AC coil draws its control voltage from the same supply as the pilot devices; verify the transformer rating handles the inrush if multiple contactors pull in simultaneously. Multi-unit packing of 12 per carton suits panel builders staging a batch of identical starters.