Siemens 3RB3123-4RB0 Relay

Siemens 3RB3123-4RB0 is an electronic overload relay from the SIRIUS 3RB3 family, designed to mount on size S0 contactors for motor protection. It covers a protected current range of 0.1 to 0.4 A and is driven by a 24 V DC coil drawing approximately 0.4 A. The unit provides a single auxiliary contact pair (one normally open, one normally closed) for signaling or interlock circuits, and features screw terminals for both the main circuit and the auxiliary circuit. It is rated for voltages up to 690 V and offers Class 5…30 protection tolerance. Reset can be performed manually or automatically, and it includes internal ground fault detection. The enclosure offers front IP20 protection and the terminal side is IP20, with installation allowances up to 2,000 meters above sea level. This overload relay is intended to protect small and medium motors by interrupting the protected circuit when an overload is detected, helping prevent overheating and damage, and it aligns with other 3RB3 relays for streamlined panel wiring in Siemens motor control architectures.