The 3RT1045-3AG14 is a SIRIUS power contactor in size S3, rated 37 kW at 400 V in AC-2 duty — that's the category for slip-ring motor starting, where the contactor makes and breaks the rotor circuit under load. The AC-3 rating (squirrel-cage motors) is also covered; the 1 000 cycles per hour maximum at AC-3 tells you it handles frequent starting without overheating the coil or arc chamber.
Solid wire from 0.25 to 2.5 mm² (two conductors per clamp) and stranded from 10 to 50 mm² (also two per clamp). That's a wide range: the smaller solid pair covers control wiring, the larger stranded pair handles the power circuit.
Thermal and mechanical limits
The arcing time is 10 to 15 ms, and the switching frequency at AC-3 maxes out at 1 000 cycles per hour, so it's not a high-speed chopper but it's fine for normal motor starting cycles.
The auxiliary contacts are rated for 24 V at 10 A, 60 V at 2 A, 110 V at 1 A, 220 V at 0.3 A, 230 V at 6 A, 400 V at 3 A — that's a mix of resistive and inductive loads. The 230 V 6 A rating is useful for a control transformer secondary; the 24 V 10 A covers PLC outputs or relay coils. No separate auxiliary block is listed here — these are the built-in contacts on the standard S3 frame.