What it is and what it does
The Siemens SIRIUS 3RT1325-3XF48-0LA3 is a size S0 power contactor with four normally-open main contacts, rated at 7.5 kW for AC-2 duty at 400 V — that's the motor-switching rating for slip-ring or wound-rotor motors, where the load current stays high through the opening arc. The 110 V DC coil includes a built-in varistor surge suppressor, so you don't need to add an external snubber on the coil circuit. It's a current-production part, quoted to order against an RFQ.
Key ratings and what they mean for fit
The 7.5 kW AC-2 at 400 V rating governs the real motor load this contactor can switch — AC-2 is the category for starting and plugging of slip-ring motors, where the contactor must interrupt the rotor current at standstill. For AC-12 resistive loads (heater, lighting) it's rated at 10 A maximum. The coil pulls 15 W closing power and 11 W holding power at DC, so the control transformer or power supply must be sized for that inrush. Short-circuit coordination is specified: Type 2 coordination requires a gL/gG fuse rated at 25 A; Type 1 coordination allows up to 63 A. That's the fuse sizing you need to protect the contactor during a bolted fault — Type 2 means the contactor remains usable after clearing the fault, Type 1 means it may need replacement. The contactor mounts on a 35 mm DIN rail per EN 50022, either screw-fixed or snap-on, and fits a standard S0 footprint — 71 mm wide, 119 mm high, 101 mm deep. The front face carries IP20 protection (finger-safe), while the terminals themselves are rated IP00 (no protection against tools or wires). Pollution degree 3 means it's suited for industrial environments with conductive dust or moisture. Operating temperature range is -40 to +70 °C, and the maximum operating altitude is 2 000 m without derating. The main circuit terminals are screw-type, accepting up to 2x 10 mm² or 1x AWG 12 solid/stranded — the wire range is 0.25 to 2.5 mm² for the auxiliary contacts (2x conductors).