Siemens 3RT1025-1BD44 SIRIUS S0 Power Contactor — 7.5 kW AC-2, 24 VDC Coil
The AC-2 rating (7.5 kW at 400 V) governs slip-ring motor starting and reversing — the duty cycle the contactor sees in a crane or hoist panel. For plugging or inching duty, the AC-4 rating of 15.5 A at 400 V is the limit to watch. Mounts on 35 mm DIN rail per EN 50022 with a snap-on feature, or screws directly to a backplate. At 45 mm wide, it fits standard S0 panel layout — one slot in a multi-contactor grouping.
Coordination and Protection
Short-circuit protection depends on your coordination choice. With Type 1 coordination, a gL/gG 63 A fuse clears a fault without destroying the contactor — you replace the fuse and keep running. With Type 2 coordination, the 25 A gL/gG fuse limits damage to the contactor itself, so you swap both fuse and contactor after a fault. Pick the fuse to match your maintenance philosophy. The contactor carries an IP20 finger-safe enclosure on the front; the terminals themselves are IP00 — wire into a panel with covers in place. Pollution degree 3 means it is rated for conductive dust and humidity typical of industrial enclosures, not clean-room or office environments.
Wiring and Terminal Capacity
Main current circuit terminals accept screw-type connections: 2x (1 to 2.5 mm²) stranded, 2x (2.5 to 6 mm²), or up to 1x 10 mm² solid. The auxiliary contact block terminals handle 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²), max 2x 4 mm². Strip lengths and torque values follow standard Siemens S0 practice — no oddball termination. Ambient operating range is -25 to +60 °C; the contactor is rated for installation up to 2000 m altitude without derating. Side-by-side mounting is permitted — no spacing gap required, which keeps panel width tight.
Auxiliary Contact Load Ratings
The built-in auxiliary contact (1 NO + 1 NC, instantaneous) has a rated operational current of 10 A at AC-12 (resistive). For DC switching, the ratings drop with voltage: 10 A at 24 V, 2 A at 60 V, 1 A at 110 V, 0.3 A at 220 V. That 0.3 A at 220 VDC is the limit for a DC coil or indicator lamp — do not parallel loads that exceed it.
Sourcing and Availability
This is an active, current-production Siemens SIRIUS part. Sourced and quoted to order through independent distribution against an RFQ — availability and current pricing confirmed at quote time. No last-time-buy window to chase.