SIRIUS 2 Contactors Siemens SIRIUS 2 Contactors provide switching with high contact reliability, prolonged endurance, and usability in extreme conditions. The Siemens SIRIUS 2 Contactors include the 3RT devices that offer up to 2650A switching without current derating up to an ambient temperature of +55°C. SIRIUS 2 complies with all major standards and certificates.