What this part is and what it does
The Siemens 3RT2035-3XF44-0LA2 is a SIRIUS power contactor, size S2, designed for switching motor loads and resistive loads in industrial control panels. It carries a 110 VDC coil with spring-type terminals, rated for continuous duty. The main contacts are rated 40 A at 480 V and 41 A at 600 V, with a 7.5 hp rating at 230 V. This contactor mounts via screw or snap-on onto a 35 mm DIN rail per DIN EN 60715, fitting into standard panel layouts. The mounting position allows +/-180° rotation on a vertical surface and +/-22.5° tilt forward/backward, giving flexibility in tight enclosures.
Key ratings and what they mean for fit
The 40 A rating at 480 V and 41 A at 600 V are the continuous current ratings for the main contacts — these define the maximum load the contactor can carry without overheating. For motor starting (AC-3 duty), you'd typically derate; the AC-4 maximum switching frequency is 300 operations per hour, which tells you this contactor isn't meant for high-cycle jogging or plugging applications. The 110 VDC coil draws an inrush peak of 1.5 A, which matters for control transformer sizing and DC power supply selection. The coil hold-in is sustained at the rated 110 VDC; dropout voltage is typically around 70% of rated (77 VDC) — ensure your control voltage doesn't sag below that during line starts. Operating temperature range is -40 to +70 °C, suitable for most industrial environments including unheated plant floors. Storage range extends from -55 to +80 °C. The contactor includes an auxiliary switch (1 N.O. + 1 N.C. typical for this frame), which can be used for status feedback or interlocking without an add-on block.
Mechanical and electrical endurance
Mechanical life is rated at 10,000,000 operations typical, meaning the contactor itself should outlast most application cycles if switched within its electrical ratings. Arcing time is 10 to 20 ms at DC, and the contactor is designed for a DC switching range of 30 to 55 ms — this is the time the coil takes to pick up or drop out, affecting timing in safety circuits or sequential logic.
Dimensions and panel fit
Dimensions are 114 mm height, 55 mm width, 178 mm depth. The width — 55 mm — is the key panel-space figure; it occupies one standard 55 mm-wide slot on a DIN rail. Clearance requirements are 10 mm upwards, 10 mm forwards, 10 mm downwards, and 6 mm at the side — account for these when laying out adjacent devices to avoid heat buildup and arcing clearance violations.