What it is and what the ratings mean
The Siemens SIRIUS 3RT2037-3AL20-ZX95 is a size S2 power contactor from the SIRIUS family, designed for switching motor loads in industrial control panels. Its headline rating is 65 A at 480 V under AC-3 duty — that's the current it can reliably switch for a standard squirrel-cage motor during starting and running, which is the most common application for this class of contactor. The AC-3 rating is what governs fit for motor starting; a contactor's AC-1 resistive rating would be higher, but AC-3 is the number that matters for inductive motor loads. It mounts via screw and snap-on onto 35 mm DIN rail per DIN EN 60715, which is the standard for panel integration across European and global control panels. The mounting position allows +/-180° rotation on a vertical surface and +/-22.5° tilt forward/backward, giving flexibility in crowded enclosures.
Switching frequency and endurance
Rated for up to 700 switching cycles per hour under AC-3 duty, and 800 under AC-1 resistive load. That's typical for a general-purpose contactor — enough for conveyor cycling or pump starts, but not for high-speed indexing applications where you'd need a dedicated DC-operated or higher-frequency device. Mechanical endurance is listed at 10 million operating cycles typical, which is standard for the S2 frame size and reflects a well-built contactor that will outlast most panel designs.
Coil and auxiliary contacts
The magnet coil connection uses spring-type terminals, which speeds up wiring compared to screw terminals — no torque driver needed, just strip and insert. The contactor carries an auxiliary switch block (1 N/O + 1 N/C configuration from the main contact count of 18...1), so it can report its status back to a PLC or safety relay without an add-on module. The coil draws 10 A at 24 V rated value, which is the inrush; the holding current will be lower, but that's the figure to budget for your 24 VDC power supply sizing.
Clearances and thermal environment
Requires 10 mm clearance upwards, downwards, and forwards, and 6 mm at the sides for arc dissipation and airflow. Operating temperature range is -25 to +60 °C, with storage from -55 to +80 °C. The arcing time is 10 to 20 ms, which is fast enough to limit fault energy in a motor branch circuit. Dimensions are 114 mm high, 55 mm wide, and 130 mm deep — the S2 footprint is compact enough for high-density panel layouts.