What This Contactor Does in the Panel
The Siemens 3RT10351AK600ST0 is a SIRIUS S2 contactor rated 40 A at 120 VAC coil, three-pole, with screw terminals and a modified shunt ring. The 120 VAC coil (110 V 50 Hz / 120 V 60 Hz) is a common control voltage, so it slots into existing transformer-based control circuits without a separate DC supply.
Screw terminals accept stranded or solid copper — torque to the manufacturer spec for the 40 A rating. The modified shunt ring reduces inrush on the coil, which matters if the control transformer is already loaded near its VA rating. Verify the free-wheel diode or RC snubber polarity on any auxiliary contacts sharing the same coil circuit.