The Siemens SIRIUS 3RT1926-1BD00-ZX90 is a varistor-type surge suppressor rated for 127...240 V AC and 150...250 V DC, designed to clamp voltage transients across the coil of a contactor. It mounts directly onto SIRIUS contactors in frame sizes S0, S1, S2, and S3 — the common range for motor loads up to roughly 37 kW at 400 V. The multi-unit packaging ships 10 pieces per order code, which is typical for panel builders who fit one per contactor across a line.
The 3RT1926-1BD00-ZX90 is listed as a phased-out product. The official Siemens successor is the SIRIUS 3RT2 series surge suppressor, which shares the same voltage range and mounting footprint for S0 through S3 contactors. For a BOM line that was specified around this order code, the 3RT2 variant is the drop-in replacement — same function, same panel cutout, same wiring.
The 127...240 V AC / 150...250 V DC voltage range covers the most common control supply voltages in industrial panels — 120 V and 230 V AC, plus 125 V and 220 V DC. The varistor clamps the inductive kick when the contactor coil de-energizes, protecting nearby PLC outputs and DC power supplies from voltage spikes. The S0 through S3 frame compatibility means it fits the same contactor sizes that handle motor currents from about 9 A (S0) up to roughly 65 A (S3) in AC-3 duty. If your panel uses SIRIUS contactors in those sizes, this suppressor clips directly onto the coil terminals without extra wiring or DIN-rail space.