The AC-4 breaking current of 66 A at 400 V covers reversing and plugging duty, where the contactor must interrupt full motor current. These ratings define the real load it can carry, not just a theoretical maximum.
Side-by-side mounting is permitted, which matters when packing multiple contactors into a tight enclosure. The 70 mm width and 146 mm height fit the S3 footprint; depth of 152 mm includes the arc chamber and terminal clearance. Screw-type terminals on the main circuit accept 2x (10…50 mm²) stranded cable; control terminals accept 2x (0.5…1.5 mm²) solid or 2x (0.75…2.5 mm²) stranded. IP20 on the front with cover or box terminal; IP00 at the terminal itself — so the panel enclosure provides the overall IP rating.
The AC-4 rating of 66 A at 400 V is the severe-duty figure; if your application involves frequent reversing or inching, that 66 A is the limit, not the AC-2 kW. The coil operates on DC with a pick-up time of 14…20 ms and an arcing time of 10…15 ms. AC-4 drops to 300 per hour due to the higher arc stress.