Siemens 3RV2821-4BD10 Soft Starter Controller Module

Siemens 3RV2821-4BD10 is a SIRIUS 3RV2 motor protection circuit breaker in frame size S0, designed for transformer protection and listed under UL 489 with CSA C22.2 No. 5-02 compliance. The three-pole device accepts up to 690 V AC and carries a nominal current rating of 20 A, featuring an integrated thermal overload release rated at 20 A and a magnetic short‑circuit release rated at 325 A to interrupt fault currents quickly. Its electrical connections use screw terminals and the housing measures about 45 mm wide by 144 mm high by 97 mm deep, yielding a compact footprint suitable for panel mounting in tight control cabinets. Typical applications include protecting transformers and motors in industrial automation, switchgear assemblies, and other heavy-duty electrical installations where compact, UL-listed protection is required to meet safety and performance standards while enabling reliable tripping under overload or short-circuit conditions.