What this breaker is and what it does
The Siemens 5SY4302-7 is a 3-pole miniature circuit breaker from the SENTRON series, designed for branch-circuit protection in industrial control panels and distribution boards. It carries a C-curve tripping characteristic, meaning it tolerates moderate inrush currents — typical for motor starters, contactor coils, and small transformers — before tripping magnetically at 5 to 10 times rated current. The part is rated for 400 V AC and 60 V DC, with a frequency range of 50/60 Hz.
Breaking capacity — what the ratings mean for fit
The 5SY4302-7 is certified under three standards, each with a different interrupting rating. Per EN 60898-1 it is rated 10 kA; per IEC 60947-2 it is rated 35 kA; and per UL 1077 / CSA C22.2 No.235 it is rated 5 kA. For DC circuits, the IEC 60947-2 rating is 15 kA at 72 V DC maximum. These numbers govern where the breaker can be installed: the 35 kA IEC rating suits high-fault industrial mains, while the 5 kA UL figure limits it to supplementary protection in North American panels. The 10 kA EN rating covers most European residential and light commercial distribution boards.
Mounting and environmental notes
The breaker occupies 3 modular width units (54 mm,) and installs on a DIN rail via the quick-assembly system. Mounting position is any; installation depth is 70 mm, overall depth 76 mm. The enclosure is IP20 with connected conductors, rated for pollution degree 3 and overvoltage category III. Ambient temperature range is -40 °C to 75 °C, with humidity limits per. The housing is halogen-free and silicon-free, which matters for clean-room or high-reliability environments where outgassing can contaminate contacts or optics.