The 3RT1066-6QP35: The 300 A rating at 24 V rated value is the DC-1 or resistive-load current at that coil voltage — for motor duty you'll want to check the AC-3 rating (not listed in this spec set, but the S10 frame typically carries a lower AC-3 value). The coil itself is rated 200...277 V AC, screw-type terminals, so it pulls in on standard control voltages across that range. Operating frequency limits are given per duty class: 750 operations/hour at AC-1 maximum (resistive), 250 at AC-2, 500 at AC-3, and 130 at AC-4. The contactor accepts stranded conductors from 70 to 240 mm² on the main power terminals, which is a wide range — it'll take a 70 mm² cable for a 300 A feeder or a 240 mm² for a high-current bus. The solid/stranded auxiliary terminal range is 2x (0.5...1.5 mm²) or 2x (0.75...2.5 mm²), max 2x (0.75...4 mm²), so control wiring is straightforward with standard ferrules.
Mounting is by screw fixing — no DIN rail clip on this S10 frame, so you'll bolt it to a backplate or mounting rail. Dimensions are 210 mm high, 165 mm wide, 202 mm deep — that's a substantial footprint, so check your gland plate and wireway clearance before committing the panel layout. Protection rating is IP00 overall, with IP20 on the front when a cover or box terminal is fitted. That means the contactor itself is not touch-safe on the sides or rear — it needs to live inside a locked enclosure or behind a panel door.