The Siemens SIRIUS 3RT5926-1BC00 is a varistor-type surge suppressor designed to clip onto S0-size contactors, protecting the coil circuit from voltage transients. It handles control supply voltages of 48 to 127 V AC at both 50 and 60 Hz, and 70 to 150 V DC, making it a single-component fit for panels that mix AC and DC control circuits.
The 48-127 V AC range (both 50 and 60 Hz) covers standard 110-120 V control transformers common in North American panels and 48 V control loops used in European installations. The 70-150 V DC range accommodates 110 V DC control buses and 125 V DC battery-backed systems found in substations and switchgear. Because it's a varistor, it clamps the voltage spike rather than filtering it — suitable for suppressing inductive kick from contactor coils, but not for continuous overvoltage protection.
Clip-on fastening to S0-size contactors means no DIN-rail space is consumed and no additional wiring is needed beyond the coil terminals. The suppressor mounts in any position, so orientation in a crowded panel isn't a constraint.
Compliance documentation
The part carries the SIRIUS brand designation and is designed for use with Siemens contactors, so the usual manufacturer declarations (CE, UKCA) apply per the SIRIUS product family documentation.