The Siemens SENTRON 5SY8303-7 is a 3-pole miniature circuit breaker (MCB) with a C-tripping characteristic rated at 3 A at 230/400 V AC, 50/60 Hz. Rated current derates with ambient temperature: 3 A at 45 °C, 2.92 A at 50 °C, 2.85 A at 55 °C. In a hot panel — say next to a drive or transformer — the actual continuous load should stay under the derated figure. The 3-module-width footprint (54 mm wide, 90 mm tall, 76 mm deep, 70 mm installation depth) snaps onto standard DIN rail, and the mounting position is any orientation.
The 5 kA rating per UL 1077 and CSA C22.2 No. 235 covers North American supplementary protection applications. Vibration resistance per IEC 60068-2-6 (±1 mm at 5 to 25 Hz; 50 m/s² at 25 to 150 Hz) means it holds up on a machine frame or in a mobile equipment panel. Halogen-free and silicon-free construction, sealable, with touch protection and combined top/bottom terminals — no neutral conductor switching on this 3P variant.