SIRIUS Size S0 power contactor, 48 V coil
The Siemens 3RT1024-1AH20 is a SIRIUS power contactor in the Size S0 frame, designed for switching motor loads in industrial control panels. It carries a 48 V rated control supply voltage at both 50 Hz and 60 Hz, and is rated for 7.5 kW at both 500 V and 690 V in AC-3 duty — meaning it handles typical 3-phase induction motors up to that power level at those line voltages. The contactor mounts via screw or snap-on onto 35 mm DIN rail per EN 50022, fitting standard panel layouts without extra adapters.
Key ratings and what they mean for fit
The AC-4 rating of 12.5 A at 400 V matters if you are switching loads with frequent inching or plugging — AC-4 is the severe duty cycle for reversing and jogging, where the contacts make and break locked-rotor current. For less demanding applications, the AC-2 rating of 5.5 kW at 400 V covers slip-ring motor starting. The auxiliary contact block handles 10 A at 24 V, 6 A at 230 V, and 3 A at 400 V (AC-12/AC-15 type loads), so it can drive small contactors or PLC outputs directly without an interposing relay. Mechanical endurance is rated at 10 million operating cycles typical, which suits high-throughput conveyor or packaging lines where the contactor cycles every few seconds. Pollution degree 3 means the contactor tolerates conductive dust and humidity typical of factory floors — no need for an extra enclosure in most industrial environments, though the front face is IP20 and the terminal area is IP00, so finger-safe wiring is only at the front. Side-by-side mounting is permitted without derating, which saves DIN rail space in dense panels — the 45 mm width per unit means you can pack multiple contactors without forced gaps. Operating temperature range of -25 to +60 °C covers most heated or unheated plant rooms, but if your panel sits in a non-climate-controlled space near a furnace or in direct sun, verify the internal panel temperature stays below 60 °C.
Termination and wiring
Main circuit terminals are screw-type, accepting 2x (1 to 2.5 mm²) solid or 2x (2.5 to 6 mm²) stranded, with a maximum of 2x 10 mm² per terminal. The auxiliary contact terminals accept 2x (0.5 to 1.5 mm²) solid or 2x (0.75 to 2.5 mm²) stranded, max 2x (0.75 to 4 mm²). AWG equivalents for the main contacts are 2x (16 to 12) solid, 2x (14 to 10) stranded, or 1x 8. Strip lengths are standard for the terminal design — no special crimp tooling needed beyond a standard screwdriver.
Short-circuit coordination
For Type 2 coordination (no damage to the contactor after a short circuit), the required upstream fuse is gL/gG 25 A. For Type 1 coordination (contactor may need replacement but the circuit is cleared), use a gL/gG 63 A fuse. This matters when you are designing a panel that must meet IEC 60947-4-1 coordination requirements — the 25 A fuse limit means you cannot oversize the branch protection without risking the contactor in a fault event.