The 3RT1046-3KJ84-0LA0: The AC-3 rating of 55 kW at 500 V is the headline motor-switching figure — it tells you this contactor can handle the inrush and break the running current of a standard squirrel-cage motor up to that power. At 400 V, the AC-2 rating of 45 kW covers slip-ring motor applications where the starting current is lower but the switching frequency may be higher. The mechanical life of 10,000,000 operations is typical for this frame size; the electrical life will be lower and depends on the switched current and duty class. The control circuit is rated at 72 V (likely AC or DC — the evidence does not specify the kind, so verify against your control transformer or DC supply). The auxiliary contact ratings are given at several voltages: 10 A at 24 V, 6 A at 230 V, 3 A at 400 V, and 1 A at 110 V. These are the maximum continuous currents the auxiliary contacts can carry at those voltages; for inductive loads like contactor coils or small relays, derate per the manufacturer's curve.
Side-by-side mounting is permitted, which is useful for building compact motor starter assemblies. The main circuit terminals are screw-type, accepting 2x (10...50 mm²) stranded or 2x (2.5...16 mm²) solid/stranded. The auxiliary terminals accept 2x (0.25...2.5 mm²) solid. The dimensions are 145 mm high, 95 mm wide, and 191 mm deep — the width is the critical panel-space dimension when laying out multiple contactors side by side.