The Siemens SENTRON 5SY6302-8 is a 3-pole miniature circuit breaker (MCB) with a D tripping characteristic, rated at 2 A at 400 V AC. It breaks 6 kA per EN 60898 for general distribution panels and 30 kA per IEC 60947-2 for industrial feeder duty, so you can use it in a sub-distribution board or a machine control cabinet without worrying about the fault level.
The 3-pole body takes 3 width units (54 mm wide), and the 76 mm depth leaves room for wiring behind a shallow enclosure door. Any mounting position works, and the terminals accept top and bottom combined feed, so you can loop the supply through without extra busbars.
The D-curve trips magnetically between 10× and 20× In, so at 2 A the magnetic trip threshold is 20–40 A. That keeps it from dropping out on a motor start or a capacitive load surge. The 6 kA breaking capacity under EN 60898 covers most commercial and light-industrial panels; if your transformer-fed board has a higher prospective fault current, the 30 kA rating under IEC 60947-2 gives you the headroom without changing the breaker footprint. For DC circuits, it's rated up to 72 V — fine for control-voltage loops or small DC drives.
Halogen-free and silicon-free construction, so it won't outgas corrosive compounds in a sealed enclosure or near sensitive contacts.