Siemens 3RB1055-2FW0 Electronic Overload Relay, 50-200A, Cla

The Siemens 3RB1055-2FW0 is an electronic overload relay rated 50-200A, class 20, size S6. It includes a winding-type transformer for internal power supply. The class 20 trip curve means it allows a 20-second overload before tripping at 7.2× rated current — a common choice for motor starting duty where longer inrush times are needed, such as high-inertia loads like fans or centrifuges. The 50-200A range covers medium-to-large motors in the 22-90 kW ballpark at 400 V, depending on full-load current. The relay mounts directly on a 3RT105 contactor or can be installed individually on a 35 mm top-hat DIN rail, with manual reset. That dual-mount flexibility is useful for panel builders who want to pre-wire the contactor/overload pair on the bench before sliding it into the enclosure.