Motor ratings — what the duty classes mean
The 3RT1024-3BP40: The headline motor-switching numbers: 5.5 kW at 400 V in AC-2 duty, and 7.5 kW at both 500 V and 690 V. AC-2 is the standard for slip-ring motors and moderate-load switching — it's less demanding than AC-4 (plugging/inching) but more than AC-3 (squirrel-cage starting). For AC-4 at 400 V, the contactor is rated 12.5 A, which translates to roughly 5.5 kW for reversing or jogging applications where the contacts break full-load current repeatedly.
Coil and control circuit
The 24 V DC coil draws 5.4 W for both closing and holding — a single-wattage coil, not a two-stage economy type. That means the PLC or relay driving it needs to supply the full 5.4 W continuously, not just a momentary inrush. The auxiliary contact ratings are given across several voltages: 10 A at 24 V, 6 A at 230 V, 3 A at 400 V, and 0.3 A at 220 V DC — the DC switching capability drops sharply with voltage, which is typical for a contactor without arc chutes on the auxiliaries.
Short-circuit coordination and protection
For Type 2 coordination (no damage to the contactor after a short-circuit), Siemens specifies a gL/gG fuse of 25 A. For Type 1 coordination (contactor may need replacement but the installation is safe), the fuse can go up to 63 A. This matters when you're coordinating with upstream motor protection — the 25 A Type 2 limit means you can't just throw a 40 A breaker ahead of it and call it done.
Mounting and environmental constraints
Mounts on 35 mm DIN rail per EN 50022, screw or snap-on. Side-by-side mounting is allowed without derating — no gap required between contactors. Operating temperature is -25 to +60 °C, pollution degree 3 (industrial environment with conductive or dry non-conductive pollution). Maximum altitude 2,000 m without derating. Front face is IP20 (finger-safe), terminals are IP00 (tool access only).
Wiring and terminal capacity
Main circuit terminals accept 2x (0.25 to 2.5 mm²) solid, or 2x (1 to 2.5 mm²) and 2x (2.5 to 6 mm²) stranded, up to a maximum of 2x 10 mm². AWG equivalents: 2x (16 to 12), 2x (14 to 10), and 1x 8. The auxiliary contact block on the side has a 6 mm clearance requirement.