The Siemens 3RT1647-1AK61 is a SIRIUS capacitor contactor rated for AC-6 duty at 50 kVAr / 400 V — that means it's built specifically for switching power-factor-correction capacitor banks, not general motor loads. The AC-6 utilization category accounts for the high inrush current when energizing a discharged capacitor, which can reach 100x the rated current for a few milliseconds. A standard contactor would weld its contacts under that surge. The single NO auxiliary contact (1 NO) is available for status feedback to the PLC or to interlock the capacitor bank controller.
The 70 mm width means it occupies four standard 17.5 mm module spaces — plan your enclosure rail fill accordingly. Main and auxiliary circuits both terminate at screw-type terminals.
Dimensions: 167 mm high, 70 mm wide, 183 mm deep. The depth is the key fit dimension for shallow enclosures — 183 mm means it needs clearance behind the mounting rail for the contactor body and wiring. Protection class IP00 for the terminal area, IP20 on the front with the cover or box terminal installed. In a typical IP54 or IP65 panel this is fine, but if the contactor is mounted exposed, the front cover must be fitted to meet finger-safe requirements.