Siemens 3RV1042-4FB10 Soft Starter For 3-Phase AC Motors

Siemens 3RV1042-4FB10 is a SIRIUS motor starter protector that mounts on a standard DIN rail within motor-control panels to protect 3-phase AC motors. It integrates overload protection with a compact circuit-breaker function for motor circuits in a single device. The unit is specified for a continuous current range of 28 to 40 A (S3 A-release) and provides short-circuit protection up to 520 A, with motor protection up to 100 kA, Class 20. Weighing about 4.883 lb (approximately 2.22 kg) and RoHS compliant since 2006, the device is manufactured in Germany and carries the market-facing article number 3RV1042-4FB10 (also listed as 3RV10424FB10). This model is part of Siemens’ legacy SIRIUS 3RV motor protection family, with retailers noting a preferred successor in the 3RV2 family (for instance 3RV2042-4FB10). The compact form and DIN rail compatibility make it suitable for control panels in industrial automation, guarding small-to-medium motor loads while simplifying wiring and protection coordination.