Power Contactor for Motor and Resistive Loads
The Siemens SIRIUS 3RT1025-3KF44-0LA0 is a size S0 power contactor with a 110 V DC coil, designed for switching motor loads and resistive circuits in industrial control panels. It mounts on a 35 mm DIN rail per DIN EN 50022, using either screw or snap-on fastening, and is rated for side-by-side mounting to save panel width. For motor duty, the contactor delivers 7.5 kW at AC-2 (400 V) and 15.5 A at AC-4 (400 V), covering standard squirrel-cage motor starting and plugging/inching applications. Resistive load handling reaches 10 A at AC-12 maximum. The coil draws 23 W on closing and 7 W holding, with a varistor surge suppressor built in for DC switching. The auxiliary and control circuit uses spring-loaded terminals; the main power circuit uses screw-type terminals, accepting solid or stranded wire up to 2x 10 mm².
Coordination and Protection
Type 2 coordination requires a gL/gG fuse rated 25 A; Type 1 coordination requires 63 A. The contactor is rated for pollution degree 3 and operates from -40 °C to +70 °C, with IP20 protection on the front and IP00 at the terminals. The auxiliary contact block supports DC switching at 110 V (1 A), 24 V (10 A), 60 V (2 A), 220 V (0.3 A), 230 V (6 A), 400 V (3 A), 500 V (10 kW), and 690 V (11 kW). Mechanical life is rated at 10,000,000 operations typical.