Siemens 5SY4304-7CV — 3-pole C4 MCB for industrial panel protection
The Siemens 5SY4304-7CV is a 3-pole miniature circuit breaker with a C-curve trip characteristic, rated 4 A and a 15 kA breaking capacity at 400 V AC per IEC 60947-2. It is designed for mechanical engineering and industrial panel applications, protecting branch circuits against overload and short-circuit faults. DC operation is limited to 72 V maximum, so this is an AC-primary device — do not spec it for a DC bus above that voltage.
For a BOM freeze or line-down replacement, this part is a direct drop-in fit for any panel specified with the Siemens 5SY4 series 3-pole C-curve breakers. No rewiring or busbar rework needed if the existing breaker is the same pole count and form factor.
Sealable — lockable with a padlock for lockout/tagout compliance. In a densely packed enclosure, account for this self-heating; the breaker's own derating curve (95 % at 55 °C, 55 % at 70 °C, 35 % at 75 °C) governs the actual continuous current you can pull.
Vibration resistance per IEC 60068-2-6: ±1 mm at 5–25 Hz, 50 m/s² at 25–150 Hz. Mechanical service life typical 10,000 operating cycles — sufficient for most industrial switching duties where the breaker is cycled infrequently (maintenance isolation, not daily load switching). Degree of pollution 3, overvoltage category III — suitable for fixed industrial installations where conductive pollution or condensation may occur.