Contactors - 3RT Range, Screw Connections The 3RT Range of Siemens Contactors. All models are highly reliable and extremely good quality. Screw Connection All models vary with Current rating and Voltage. Various NO/NC Values Siemens Sirius Range Contactor & Control Relays Siemens control gear for feeders up to 5.5kW. The complementary nature of the devices allows fast and simple assembly, for example, of motor starters and reversers. A perfect match between contactors, overloads, circuit breakers and accessories for the same power ratings provides a uniform panel appearance and the standard widths with no side-by-side mounting derating allows for space saving.