What this 4 A D-curve MCB is for
The Siemens SENTRON 5SY4604-8 is a 4-pole (3P+N) miniature circuit breaker rated 4 A with a D tripping characteristic, designed for protecting circuits against overloads and short circuits in industrial control panels and mechanical engineering applications. The D-curve means it tolerates high inrush currents — typically used for motor, transformer, or welding equipment circuits where the startup surge would nuisance-trip a B or C curve breaker. The 4 A rating at 35 °C is the base; at elevated panel temperatures it derates to 3.71 A at 45 °C, 3.61 A at 50 °C, 3.5 A at 55 °C, and 3.39 A at 60 °C, so factor the ambient inside your enclosure when sizing.
Breaking capacity and ratings
Rated breaking capacity is 10 kA per EN 60898, which covers most commercial and light industrial distribution boards. For industrial applications where fault currents are higher, the IEC 60947-2 rating of 35 kA applies — that's the number to use when the breaker is specified into a machine control panel with a high-capacity transformer upstream. DC breaking capacity is 15 kA per IEC 60947-2, covering battery-backed or rectifier-fed circuits.
Mounting and integration
Snaps onto DIN rail via the quick assembly system, occupies 4 modular width units (72 mm wide). Mounting position is any, so it fits vertical or horizontal busbar arrangements. Installation depth is 70 mm behind the panel surface; overall depth is 76 mm. Combined terminals top and bottom accept the same conductor range — no special order for feed direction. Touch protection is built in, pollution degree 3 (conductive pollution typical in industrial enclosures).