Star-delta motor starting, pre-assembled
The Siemens 3RA2445-8XF32-1NB3 is a factory-assembled SIRIUS contactor assembly for star-delta (wye-delta) motor starting. It ships with three contactors: two 3RT2045-1NB30 units for the line and star legs, and one 3RT2036-1NB30 for the delta leg, plus the interconnecting RS assembly kit 3RA2943-2C. Rated for 75 kW at 400 V and 110 kW at 690 V in AC-3 duty, this assembly handles the transition from star to delta without the user having to size and wire individual contactors and the timing relay. The built-in varistor surge suppressor snubs coil transients at the DC magnet coil terminals.
This gives panel builders room to fit it into tight enclosures without reworking the backplate. Dimensions are 180 mm high, 220 mm wide, and 244 mm deep — the depth is the dimension to watch when fitting into shallow enclosures. Clearance distances around the assembly: 10 mm upwards, forwards, downwards, and to the side; 0 mm backwards. The zero backward clearance means it can sit flush against the back panel or a busbar support without additional spacing.
Duty ratings and protection coordination
The assembly is rated for a maximum of 1,000 switching operations per hour in AC-3 duty. Mechanical life is 10 million operations typical for the contactors — the limiting factor in star-delta service is usually the delta contactor's electrical life during the transition, not the mechanical endurance. For branch circuit protection, Siemens specifies gG NH 3NA, DIAZED 5SB, or NEOZED 5SE fuses rated at 160 A. The DC magnet coil draws 154 W closing power at 20 to 33 V DC. Vibration resistance is specified at 10.6 g / 5 ms and 6.3 g / 10 ms for AC, which covers most industrial motor-drive applications including conveyors and pumps. The power factor at 50/60 Hz is 0.95.
Lifecycle and sourcing
Substance prohibitance date is 03/01/2017, confirming RoHS and REACH compliance. No auxiliary switch extension or bus communication module is fitted as standard — the assembly is a standalone star-delta starter with screw-type control terminals.