SIRIUS S0 power contactor, 24 V coil, screw terminals
The Siemens 3RT1025-1AC20-ZW96 is a SIRIUS S0-size power contactor with a 24 V 50/60 Hz coil, designed for screw and snap-on mounting onto 35 mm DIN rail per EN 50022. Its 45 mm width and 85 mm height fit standard panel layouts, and the IP20 front face allows safe operation in enclosed control cabinets. Rated for motor switching in AC-2 duty at 7.5 kW (400 V) and AC-4 at 15.5 A (400 V), this contactor handles reversing, plugging, and inching applications common on conveyor and pump lines. The 24 V coil draws its control voltage from a standard transformer or PLC output, and the operating range holds from 0.8 to 1.1 × rated voltage at 50 Hz and 0.85 to 1.1 at 60 Hz.
Main circuit terminals accept screw-type connections: 2 × (0.5 to 1.5 mm²) solid, 2 × (0.75 to 2.5 mm²) stranded, and up to 2 × (0.75 to 4 mm²) maximum. AWG equivalents are 2 × (16 to 12), 2 × (14 to 10), and 1 × 8. Auxiliary and control wiring uses the same terminal range, simplifying panel wire-up. Side-by-side mounting is permitted with zero lateral clearance, saving rail space. When ganged, the 6 mm spacing to adjacent devices or enclosure walls must be maintained for heat dissipation.
These values guide the selection of branch-circuit protection for the motor starter assembly.
The S0 frame size is a common Siemens SIRIUS platform, ensuring spare parts and accessories (coil, auxiliary contact blocks, surge suppressors) are widely stocked.