The Siemens SIRIUS 3RU series thermal overload relays provide current-dependent protection for motors and feeder cables against overload and phase failure. Designed to monitor the main circuit, they trip according to a Class 10 characteristic under IEC 60947-4-1, meaning they disconnect the load within 10 seconds or less at 7.2 times the rated current. The relays are mechanically and electrically matched to Siemens 3RT contactors, allowing direct, space-saving mounting for complete load feeder assemblies. They are available with screw or spring-type terminals for secure, vibration-resistant wiring. Each relay includes manual or automatic reset selection, auxiliary contacts (1 NO and 1 NC), and a TEST function for verifying contact operation. Indicators show the device status at a glance. With approvals for global use and operation in environments from –40 to +70 °C, the 3RU relays are suitable for industrial control panels, motor starters, and applications requiring dependable overload protection.
