SIRIUS S0 power contactor for motor and resistive loads
The Siemens 3RT1025-1BG44 is a SIRIUS S0-frame power contactor rated for motor switching at 7.5 kW in AC-2 duty at 400 V, and 15.5 A in AC-4 duty at the same voltage. That AC-2 rating covers slip-ring motor reversing and inching applications where the contactor sees moderate arcing; the AC-4 figure governs plugging and jogging duty with higher electrical wear. For resistive or lightly inductive loads, the AC-12 continuous current rating is 10 A. The contactor also carries kW ratings at higher line voltages: 10 kW at 500 V and 11 kW at 690 V, which makes it usable on 480 V and 600 V class systems common in North American and export panels. DC switching capability is specified across four voltages — 10 A at 24 V, 2 A at 60 V, 1 A at 110 V, and 0.3 A at 220 V — covering battery-backed control circuits and DC motor brake coils.
Mounting and panel integration
Mounts via screw or snap-on onto 35 mm standard rail per DIN EN 50022. The S0 frame is 45 mm wide, 85 mm tall, and 150 mm deep — a compact footprint that leaves room for auxiliary contact blocks on the side. Side-by-side mounting is permitted with 6 mm spacing to adjacent devices, so you can gang multiple contactors on a single rail segment without derating for heat buildup. Main circuit terminals accept screw-type connections: solid conductors from 0.5 to 4 mm² (2x per clamp), and stranded up to 10 mm². AWG equivalents are 2x 16–12 solid, 2x 14–10 stranded, and 1x 8. The control circuit terminals use a separate solid range of 0.5–1.5 mm² and stranded 0.75–2.5 mm². Pollution degree 3 rating means it's suited for industrial environments with conductive dust or condensation.