The 3RT5926-1BD00 is a varistor-type surge suppressor from the Siemens SIRIUS family, designed to mount directly onto contactors in frame sizes S0 through S3. It suppresses voltage spikes across the coil of AC/DC-operated contactors, protecting the control circuit from inductive kickback that would otherwise damage PLC outputs or relay contacts.
Kit completeness check
This is a single varistor module — no mounting bracket or hardware is needed; it clips onto the contactor's coil terminals. The kit is complete as shipped.