What It Is and Where It Fits
The Siemens SIRIUS 3RT1026-1AG20 is a power contactor in the S0 frame size, rated for switching motor loads in industrial control panels. It mounts via screw or snap-on onto a 35 mm DIN rail per EN 50022, so it integrates directly into a standard panel layout without adapter plates.
Key Ratings and What They Mean for Fit
The AC-2 rating at 400 V is 11 kW, which covers wound-rotor motor switching where the contactor makes and breaks under load. The AC-4 rating at 400 V is 15.5 A, for reversing or inching duty where the contactor handles the full locked-rotor current. For a buyer verifying BOM fit, the AC-2 power figure is the one that governs the motor nameplate; the AC-4 current figure governs the worst-case switching stress. The contactor is rated for pollution degree 3, meaning it's suitable for the typical industrial environment where conductive pollution or dry non-conductive pollution that becomes conductive due to condensation may occur. That matches the IP20 front / IP00 terminal enclosure — the terminals are not sealed, so the panel itself must provide the environmental protection. Mechanical endurance is listed at 10,000,000 operating cycles typical. That's the mechanical life of the contactor assembly; electrical life will be lower and depends on the switching current and voltage per the manufacturer's derating curves. The operating temperature range is -25 to +60 °C during operation, which covers most indoor panel environments. Side-by-side mounting is permitted, so no derating for zero-gap spacing.
Termination and Wiring
Main and auxiliary/control circuits use screw-type terminals. The main circuit accepts solid conductors: 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), max 2x (0.75 to 4 mm²). For stranded or ferruled conductors: 2x (1 to 2.5 mm²), 2x (2.5 to 6 mm²), max 2x 10 mm². AWG equivalents are 2x (16 to 12), 2x (14 to 10), 1x 8 for the main contacts, and 2x (20 to 16), 2x (18 to 14), 1x 12 for auxiliary contacts.
Fuse Coordination and Short-Circuit Protection
For type 2 coordination (no damage to the contactor after a short circuit), the required fuse is gL/gG 35 A. For type 1 coordination (contactor may need replacement after a fault), the fuse can be up to 100 A gL/gG. This gives the panel designer flexibility: use 35 A fuses if you want to avoid replacing the contactor after a rare fault, or use a higher rating if the upstream protection is already set.