SIRIUS S0 power contactor, 24 VDC coil
The Siemens 3RT1025-1BB40-ZW96 is a SIRIUS power contactor in the S0 frame size, designed for switching motor loads in industrial control panels. The 24 VDC coil draws 5.4 W during both closing and holding, so the control transformer can be sized for continuous draw rather than a surge peak. Screw-type terminals on both the main and auxiliary circuits — no special crimp tooling needed for the panel build.
Motor switching ratings and coordination
Rated at 7.5 kW in AC-2 duty at 400 V — that covers slip-ring motor starting and braking applications where the contactor makes and breaks under load. For AC-4 duty (plugging, inching, reversing) the limit is 15.5 A at 400 V, which is the figure to use when the application cycles the motor against a locked rotor. At 500 V the contactor handles 10 kW; at 690 V it handles 11 kW. Type 1 coordination requires a 63 A gL/gG fuse upstream; Type 2 coordination needs a 25 A gL/gG fuse. The pollution degree 3 rating means it's suited for industrial environments with conductive dust or condensation — no derating for typical factory-floor conditions.
Mounting and integration
Snap-on mounting onto 35 mm DIN rail per EN 50022, or screw-fixed to a backplate. The 45 mm width and 85 mm height fit standard S0 footprint; depth is 101 mm including coil terminals. Side-by-side mounting is permitted, so multiple contactors pack tightly on the rail without derating. The front face carries an IP20 rating — safe for finger contact in an enclosed panel; the terminal area is IP00, so live parts are exposed if the contactor is mounted outside a cabinet. Operating temperature range is -25 to +60 °C.