What this contactor is and where it fits
The Siemens SIRIUS 3RT2035-1AP00-1AA0 is a size S2 power contactor, rated for 40 A at 480 V in AC-3 duty — that's the motor-switching rating, so it handles a 40 A induction motor load at that voltage without welding the main contacts. It mounts on a 35 mm DIN rail per DIN EN 60715, using either the screw or snap-on fastening method — common in IEC-style panels where you're building a motor starter cluster or a feeder group. The coil termination is screw-type, and the contactor carries an auxiliary switch block ready for add-on modules, so it's set up for a standard three-wire control scheme right out of the box.
Key ratings and what they mean for your panel
AC-3 maximum switching frequency is 1 000 operations per hour — that's the motor-starting duty cycle; if you're cycling a conveyor or a pump more often than once every 3.6 seconds, you'll need to step up to a larger frame or a dedicated switching contactor. For resistive loads (AC-1), it can handle 1 200 ops/h; for the heavier AC-4 plugging/inching duty, it drops to 300 ops/h — the arcing time sits at 10 to 20 ms, which is typical for this class and tells you the arc chute is sized for the 40 A break. Operating temperature range is -25 to +60 °C, with storage from -55 to +80 °C — so it's fine in an unheated enclosure in a cold warehouse, but you'll want to keep it out of direct sun on a hot roof. Mechanical life is listed at 10 000 000 typical operations — that's the coil and armature wearing out, not the contacts. The main contact electrical life is 18 to 1 million operations depending on load current and duty, so on a 40 A motor starting once a minute you'll get years of service before the contacts need attention.
Integration and wiring
Dimensions are 55 mm wide, 114 mm high, and 130 mm deep — the depth is the key number for enclosure depth planning: you need at least 130 mm from the DIN rail face to the back wall, plus clearance for wiring and any auxiliary block. Clearance spacings: 10 mm upwards, 10 mm forwards, 10 mm downwards, and 6 mm at the side — so you can pack contactors tight side-to-side, but you need a finger's width top and bottom for arc gas venting and cooling. Main power terminals accept 2x 0.5 to 1.5 mm² solid/stranded or 2x 0.75 to 2.5 mm² — that's fine for 40 A motor feeders with standard ring or fork terminals. The coil terminals are screw-type, so no special crimp tool needed.