What This Part Is and Where It Fits
The Siemens 3RT1026-3AP08-1MA2 is a SIRIUS power contactor in the S0 frame size, with three main poles for switching three-phase motor loads. It carries a rated motor power of 11 kW at 400 V under AC-3 duty, which covers the majority of standard induction motor starting applications — pumps, fans, conveyors, compressors — where the contactor makes and breaks the load under normal running conditions. The contactor mounts via screw or snap-on onto a 35 mm DIN rail per DIN EN 50022, fitting standard industrial control panels. At 45 mm wide and 85 mm tall, it occupies a single module width on the rail, leaving space alongside for overload relays and auxiliary contact blocks.
Key Ratings and What They Mean for Your Circuit
The headline AC-3 rating of 11 kW at 400 V means this contactor is sized for a motor drawing roughly 22 A under full load at that voltage — the AC-3 duty class covers starting and plugging, where the contactor closes on inrush and breaks the running current. For the more demanding AC-4 duty (inching, reversing, plugging with full load), the rated operating current drops to 15.5 A at 400 V, so if your application requires frequent reversing or jogging, you need to stay within that lower current envelope. The contactor is also rated for AC-2 duty at 11 kW at 400 V, covering slip-ring motor starting where the rotor resistance is varied. For resistive loads (AC-12), the maximum operating current is 10 A. The auxiliary contact ratings span from 10 A at 24 V down to 0.3 A at 220 V, covering typical PLC and relay control circuits. Short-circuit coordination is specified: with Type 2 coordination (no damage to the contactor), use a gL/gG fuse rated at 35 A. With Type 1 coordination (contactor may need replacement after a fault), the fuse can be 100 A. This lets you balance protection level against fuse size in the panel design.
Mounting, Wiring, and Environmental Fit
The contactor accepts screw-type terminals for the main current circuit, with wire ranges from 2x (0.25 to 2.5 mm²) solid up to 2x 10 mm² stranded, or 2x (16 to 12 AWG) solid. Finely stranded wire with ferrule is handled at 2x (0.25 to 1.5 mm²). Strip length and torque values follow standard Siemens SIRIUS practice for the S0 frame. The front face carries an IP20 rating, meaning finger-safe touch protection once wired — standard for inside a locked panel. The terminal area itself is rated IP00, so live parts are exposed during installation; normal practice is to de-energize before working on the terminals. Side-by-side mounting is permitted with a 6 mm gap to adjacent devices, which is typical for thermal dissipation in a dense panel layout. Operating temperature range is -25 to +60 °C, covering most indoor industrial environments. The pollution degree rating of 3 means it is suitable for environments with conductive pollution or dry non-conductive pollution that could become conductive — typical for factory floors with dust and occasional condensation.
Lifecycle and Sourcing Reality
Mechanical endurance is rated at 10 million operating cycles typical, which is the life of the contactor mechanism before wear-out — not the electrical life under load, which will be lower depending on switching frequency and current. For high-cycle applications (frequent starts per hour), factor the electrical life derating from the Siemens SIRIUS application manual.