The Siemens 3RA1445-8XB20-1AB0 is a SIRIUS wye-delta contactor assembly — a pre-configured set of three contactors and the interconnecting wiring for starting a three-phase induction motor in wye-delta transition. It is a single orderable unit, not a kit you build from individual contactors. The assembly carries three contactors in sizes S3, S3, and S2 — the two line contactors and the delta contactor are S3, the wye contactor is S2. That sizing reflects the current split: the wye leg carries roughly 58% of the line current during start, so it can be a frame smaller. Rated 150 A in AC-3 duty at 400 V, it switches motor loads up to 75 kW at 400 V, 103 kW at 500 V, and 110 kW at 690 V.
Mounts by screw fixing on a vertical surface. The assembly can be rotated ±180° around the vertical axis and tilted ±30° forward or back — useful when fitting into a tight panel corner where the gland plate or busbar routing forces an angle. Dimensions are 218 mm wide, 180 mm tall, 194 mm deep. Front protection is IP20 — finger-safe but not sealed.
For Type 1 coordination (welding allowed, but no fire or shock hazard), the fuse can be 250 A gL/gG. Type 2 is what most panel specs call for — it keeps the contactor reusable after a short-circuit clearing event. The assembly ships without a surge suppressor fitted. If the control coil is driven by a PLC output or a solid-state relay, you will want to add a suppressor across the coil terminals — the datasheet shows the available suppressor modules that clip onto the contactor. That matters for PLC feedback circuits where the contact wipes a dry logic input — gold-plated or bifurcated contacts handle the low-energy regime without oxide film issues.
The assembly covers motor ratings from 0.8 to 1.1 times the nominal current at 50 Hz, and 0.85 to 1.1 at 60 Hz. That adjustment range lets you fine-tune the overload setting to the actual motor nameplate without swapping heater packs.