The Siemens SIRIUS 3RB series is a solid-state overload relay for inverse-time delayed protection of loads with normal and heavy starting against excessive temperature rises due to overload, phase unbalance or phase failure which has a current rating up to 50 A. It has manual or automatic reset switch functionality. It has a size S2. It can be mounted with contactor mounting. The type of electrical connection for main circuit and for auxiliary circuit is through screw terminal. Due to the wide current setting ranges and various tripping characteristics, complete series of motors are covered with just a few types. It has low heat loss which makes it energy-efficient and help to reduce the temperature rise in the control cabinet.

Ambient operating temperature is -25 to +60 °C
Operating frequency is 50 to 60 Hz
Trip class is CLASS 20E