What this contactor does on your panel
The Siemens SIRIUS 3RT1326-1XX40-0VA1 is a size S0 power contactor with four normally-open main contacts and a 24 VDC coil. It switches motor loads up to 11 kW at AC-2 duty under 400 V — that's the rating that governs real induction-motor starting, not the resistive curve. The coil pulls in at 24 VDC nominal; closing power and holding power both sit at 5.4 W DC, so the control transformer or PLC output doesn't see a surge after pickup. Mounting is screw-and-snap onto 35 mm DIN rail per EN 50022. Side-by-side mounting is allowed, so you can pack multiple units without a gap spacer.
Ratings that decide the fit
AC-2 at 400 V: 11 kW. That's the motor-switching curve for slip-ring or wound-rotor motors where the contactor makes and breaks under load. For resistive loads (AC-1), the contactor can handle the full 10 A continuous per pole at 24 V DC. DC switching capability: 10 A at 24 V, 2 A at 60 V, 1 A at 110 V, 0.3 A at 220 V, and 6 A at 230 V. These numbers drop fast as voltage rises because DC arcs are harder to extinguish — the 24 V figure is the one you'll use in most control panels. The contactor is rated for pollution degree 3 (conductive pollution or dry non-conductive that becomes conductive due to condensation) and operates from -25 to +40 °C ambient.
Termination and wiring
Main circuit terminals: screw-type, accepting 2x (0.5...1.5 mm²), 2x (0.75...2.5 mm²), max 2x (0.75...4 mm²) solid or stranded. AWG equivalents: 2x (20...16), 2x (18...14), 1x 12. Auxiliary and control circuit terminals are also screw-type, same wire ranges. Finely stranded with core-end processing: 2x (0.5...1.5 mm²), 2x (0.75...2.5 mm²). Protection coordination: Type 1 requires a gL/gG fuse rated 63 A; Type 2 requires 35 A. That's the upstream short-circuit protection the contactor expects.