What this contactor is and where it fits
The Siemens 3RT1023-1AV04 is a SIRIUS power contactor in the S0 frame size, with three normally-open main contacts and a 24 VDC coil. It mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 50022, so it drops straight into a standard industrial panel without adapter plates. The 45 mm width and 85 mm height keep the footprint tight for multi-contactor rows, and side-by-side mounting is permitted — no mandatory gap derating when you pack them in.
What the ratings mean for the buyer
The AC-4 rating of 8.5 A at 400 V is the one that governs motor inrush and plugging duty — that's the current the contacts must break during reversing or jogging cycles. For straightforward AC-3 motor starting the contactor handles higher current, but the AC-4 figure is the limit when the load is switched under full load. Auxiliary contact rating at AC-12 is 10 A, which covers most PLC output and relay loads without an interposing relay. The screw-type main terminals accept 2x (1 to 2.5 mm²) solid/stranded and up to 2x 10 mm² max, so it handles standard motor feeder cables without crimping ferrules.
Panel integration notes
The contactor is IP20 on the front (finger-safe) and IP00 at the terminals — the terminals need enclosure protection in the end panel. Pollution degree 3 means it's rated for industrial environments with conductive dust or occasional condensation. Depth of 140 mm leaves enough clearance behind the DIN rail for wiring loops and ferrule insertion without crowding the gland plate.