What it is and what it does
The Siemens SIRIUS 3RT1046-1AM20 is a power contactor in size S3, designed for switching motor loads in industrial control panels. Its AC-3 rating of 55 kW at 500 V means it handles the inrush and running current of a 3-phase induction motor up to that power — the rating that governs real motor switching, not the resistive AC-1 figure. The coil is wound for 208 V AC at both 50 Hz and 60 Hz, with an operating range of 0.8 to 1.1 times rated voltage at 50 Hz and 0.85 to 1.1 at 60 Hz. That gives you a pickup window from roughly 166 V to 229 V at 50 Hz — useful to know if your control transformer sags under load. It mounts via screw or snap-on onto 35 mm or 75 mm standard DIN rail, so it drops into any IEC enclosure without special brackets. Side-by-side mounting is permitted, which keeps the row tight when you're stacking multiple contactors for a multi-motor group.
Key ratings and what they mean for fit
Beyond the headline 55 kW at 500 V, the contactor also carries a 25.4 kW rating at 690 V AC-3. That's the rating to check if your motor is on a 690 V distribution system — common in mining or marine installations. The mechanical endurance is 10,000,000 operations typical, so it's built for high-cycle applications like conveyor lines or pump stations. Switching frequency limits vary by duty: 850 operations per hour maximum in AC-3 (motor starting), 900 in AC-1 (resistive), 350 in AC-2 (slip-ring motors), and 250 in AC-4 (plugging/reversing). For a conveyor that cycles every 30 seconds, you're at 120 ops/hour — well within the AC-3 ceiling. For a reversing application, stay under 250 ops/hour. The main current circuit uses screw-type terminals, accepting solid conductors up to 4 mm² per clamp (2x 0.75 to 4 mm²) and stranded up to 50 mm² (2x 10 to 50 mm²). That's enough for the motor feeder on a 55 kW load — typically 35 mm² or 50 mm² copper, depending on run length and ambient temperature. Auxiliary contacts are rated at 10 A at 24 V, 6 A at 230 V, and 3 A at 400 V — covering the typical control circuit voltages for PLC inputs, pilot lights, and interposing relays. The contactor itself dissipates 37 W at 1000 V, which matters for thermal management inside a sealed enclosure.
Where it goes and how it fits
This is a panel-mounted component. The S3 frame measures 70 mm wide, 146 mm high, and 139 mm deep — it occupies three or four 18 mm DIN-rail module positions depending on how you count the depth clearance. IP20 on the front with the cover or box terminal installed means it's protected against finger contact in a closed panel; the terminal area itself is IP00, so live parts are exposed when the panel door is open — standard for industrial contactors. Operating temperature range is -25 to +60 °C, with storage from -55 to +80 °C. Pollution degree 3 means it's rated for conductive pollution environments — typical for factory floors with dust and humidity, not clean rooms. If your panel is in a non-climate-controlled shed in a hot climate, the +60 °C upper limit is the one to watch.