The Siemens 3RT1647-1AB01 is a capacitor contactor from the SIRIUS family, sized S3, designed specifically for switching capacitor banks. It's rated AC-6 at 50 kVAr / 400 V — that's the duty class for capacitor loads, where inrush current can hit tens of times the rated current. The 24 V, 50 Hz coil keeps it in the standard control-voltage range for many industrial panels. Three main poles, one normally open auxiliary contact, and screw terminals for both main and control wiring.
Side-by-side mounting is allowed, which saves rail space in a multi-bank capacitor setup.
Protection class is IP00 on the terminals, IP20 on the front with the cover or box terminal fitted. That means it's not a washdown part — it belongs inside a panel with a door, not out in the grease and dust of a lube route.