The Siemens SIRIUS 3RT2926-1CF00 is an RC-type surge suppressor built to clamp voltage spikes across the coil of S0-frame contactors in the 3RT2.2 family. It clips onto the contactor's front side — no wiring required — and handles control voltages from 400 to 600 V AC at 50 or 60 Hz.
The RC element suppresses the back-EMF spike when the contactor coil de-energizes. Dimensions are compact: 12 mm deep, 30 mm wide, 19 mm tall. That 12 mm depth means it adds almost no projection beyond the contactor face — the assembly still fits a standard 60 mm deep DIN-rail enclosure without crowding the gland plate. That's enough for most indoor panel environments, including non-conditioned electrical rooms. The clip-on mount and any-position orientation make it a one-handed install on the line.
Active, current-production part per Siemens. Supply channel is standard factory ordering.