The Siemens 3RA1444-8XB20-1BB4 is a SIRIUS wye-delta contactor assembly — a pre-configured set of three contactors (sizes S3, S3, S2) in a single enclosure, designed to reduce inrush current during motor starting. That translates to a 55 kW motor at 400 V, 81 kW at 500 V, and 93 kW at 690 V — the voltage-dependent power curve tells you exactly which motor frame it fits on your line. The assembly ships without a surge suppressor — you'll need to add a free-wheeling diode or RC snubber across the coil if your PLC output card doesn't include one. Mounting is screw fixing onto a vertical surface, with ±180° rotation and ±30° tilt front-to-back — enough flexibility to fit into tight panel layouts. Operating temperature range is -25 to +60 °C, storage -55 to +80 °C, and pollution degree 3 means it's rated for industrial environments with conductive pollution.
The assembly measures 218 mm wide, 207 mm deep, and 180 mm tall. That's a compact footprint for a three-contactor wye-delta set — it fits on a standard backplate without needing a separate enclosure for each contactor. Main circuit connections are screw-type terminals, sized for the 115 A AC-3 rating. The assembly has 3 poles for the main current circuit and no NC contacts on the main poles — the switching sequence is handled internally by the wye-delta logic.
The assembly includes an auxiliary switch extension option (Product Extension Auxiliary Switch: Yes), so you can add feedback contacts for status monitoring without modifying the main contactor block.