Siemens 5SY3203-7 — 2-pole C-curve MCB for 3 A branch circuits
The Siemens 5SY3203-7 is a 2-pole miniature circuit breaker from the SENTRON 5SY3 series, rated 3 A at 400 V AC with a C tripping characteristic. At 3 A it handles branch circuits feeding control transformers, contactor coils, or signal-conditioning supplies in a panel. Breaking capacity is rated at 4.5 kA per EN 60898 and 6 kA per IEC 60947-2 at 400 V AC; for DC circuits it's rated 15 kA at 72 V DC per IEC 60947-2, and 5 kA at 400 V AC per UL 1077 / CSA C22.2 No.235. That covers most industrial panel fault currents below a main distribution board.
No last-time-buy or phase-out notice is on record. For BOM-freeze planning, the 5SY3 series has broad installed base and the form factor (2-module wide, DIN-rail mount) is industry-standard, so any future replacement would share the same footprint.
Combined top and bottom terminals accept solid or stranded conductors from 0.75 mm² up to 35 mm² — a wide range that covers both control-circuit wiring (1.5 mm²) and feeder tails (10–16 mm²). The terminals are touch-protected (IP20 with conductors connected) and sealable for panel lock-out/tag-out procedures.
Coordination and selectivity note
Energy limiting class 3 means the breaker limits let-through energy well — useful for downstream component protection. Overvoltage category III suits fixed-installation distribution boards. The 5SY3 design is the standard 5SY platform with C-curve; the 5SY6 series (higher breaking capacity) exists for applications needing more fault-current headroom, but the 5SY3203-7 covers the common 3 A branch with adequate interrupting ratings for most sub-distribution panels.