The Siemens SIRIUS 3RT1035-3KB44-0LA0 is a Size S2 power contactor with a 24 VDC coil, rated for motor switching at 22 kW at 500 V in AC-3 duty.
AC-3 Motor Rating and Operating Cycle Limits
The AC-3 maximum operating cycle rate is 1,000 operations per hour, which governs how often the contactor can switch a motor load under full rated current without exceeding thermal limits. AC-4 duty (plugging/reversing) drops to 300 ops/h, reflecting the higher electrical stress of inrush handling. At 500 V AC-3, the contactor is rated for 22 kW motor load; at 690 V AC-3 it drops to 11.4 kW, consistent with the voltage derating typical of IEC contactors.
Coil and Auxiliary Contact Ratings
The 24 VDC coil draws 10 A at rated voltage; auxiliary contact ratings descend with voltage: 6 A at 230 V, 3 A at 400 V, 1 A at 110 V. The arcing time on DC is 20–25 ms, which matters for suppression circuit design — a free-wheel diode across the coil must handle the inductive kick without exceeding reverse voltage ratings.
Mounting and Terminal Details
Width is 80 mm, height 110 mm, depth 167 mm. Side-by-side mounting is permitted, saving panel width when multiple contactors share a rail. Main circuit terminals are screw-type, accepting 2x (0.75–25 mm²) stranded or 2x (0.25–2.5 mm²) solid.