What it is and what it does
The Siemens 3RT1026-3EG28-0MA3 is a SIRIUS power contactor in the S0 frame size, designed for switching motor loads in control panels. It carries an AC-2 rating of 11 kW at 400 V — that's the slip-ring motor duty where starting current and switching frequency are moderate, so it fits applications like conveyors, pumps, and compressors that don't need heavy inching. The AC-4 rating of 15.5 A at 400 V covers reversing and plugging duty, which is the tougher cycle for contact life. Mounts on a 35 mm DIN rail per EN 50022, with screw-type terminals for the main circuit. The built-in RC surge suppressor means you don't need to order a separate varistor or snubber for coil suppression on standard AC control voltages.
Ratings that matter for fit
The AC-2 motor rating (11 kW at 400 V) is the one that decides whether this contactor handles your motor load under normal start-run cycles. The AC-4 rating (15.5 A at 400 V) is the one to check if your application does frequent reversing or inching — that's where the contactor sees arcing on every break, so the current limit is lower than the AC-3 or AC-2 numbers. Short-circuit protection requires a gL/gG fuse rated at 35 A for type 2 coordination. Mechanical endurance is rated at 10 million cycles, which is typical for the S0 frame — plenty for most machine cycles over a decade. The operating temperature range of -25 °C to +60 °C covers most indoor panel environments, and the IP20 front protection means it's safe for finger contact inside a closed panel. Pollution degree 3 means it's rated for the conductive-dust environments you'd find in a typical industrial enclosure.