What it is and what it does
The Siemens 3RT1026-1AP08-0MA0 is a SIRIUS power contactor in size S0, with three normally open (NO) main contacts and no NC main contacts. It is rated for motor switching at 11 kW at 400 V in AC-2 duty, and 15.5 A at 400 V in AC-4 duty. The contactor mounts on a standard 35 mm DIN rail per DIN EN 50022, either by snapping on or screwing down, and is 45 mm wide — a standard slot in most control panels.
Key ratings and what they mean for fit
The AC-2 rating of 11 kW at 400 V means this contactor is sized for slip-ring motor starting and reversing, where the contacts close and open under load but not at locked-rotor current. The AC-4 rating of 15.5 A at 400 V covers plugging and inching duty — the tougher thermal cycle. For resistive loads (AC-1), the operating current is 10 A maximum. The auxiliary contact block provides 2 instantaneous contacts, rated at 10 A at 24 V, 6 A at 230 V, and 3 A at 400 V — enough for a PLC input or a holding circuit.
Panel integration and wiring
The contactor is 85 mm tall and 140 mm deep, with screw-type terminals on the main circuit. Wire sizes: solid conductors from 0.5 to 4 mm² (two per terminal), stranded from 1 to 10 mm² (two per terminal). AWG equivalents: 2x 16–12, 2x 14–10, 1x 8. Side-by-side mounting is allowed with 6 mm clearance to adjacent devices. Pollution degree 3 means it handles conductive dust and condensation — typical for industrial control panels. IP20 on the front, IP00 at the terminals: the front is finger-safe, but the terminals need a cover or enclosure.
Coordination and protection
For type 2 coordination (no damage to the contactor after a short circuit), use a 35 A gL/gG fuse. For type 1 coordination (contactor may need replacement), a 100 A gL/gG fuse is acceptable. The contactor is rated for a maximum altitude of 2000 m and an operating temperature range of -25 to +60 °C. Mechanical life is 10 million cycles typical.