The Siemens 5SY4120-7KK11 is a 1-pole SENTRON miniature circuit breaker with a C-curve trip characteristic, rated 10 kA breaking capacity according to DIN EN 60898-1 and 20 kA according to IEC 60947-2. The C-curve (5–10× In) handles moderate inrush from motor starters, small transformers, or lighting ballasts without nuisance tripping — the standard choice for general industrial branch circuits.
Railway-rated build, panel-ready footprint
Designed for railway applications, this MCB carries the environmental tolerance that implies: -40 °C to +75 °C operating range, pollution degree 3, and overvoltage category III. The 18 mm width (1 modular unit) clips onto any DIN rail — quick-assembly fastening, mountable in any position. Depth is 76 mm with 70 mm installation depth required behind the panel.
Breaking capacity — what the two ratings mean
The 10 kA rating under EN 60898-1 covers the standard household/commercial fault-current test. The 20 kA rating under IEC 60947-2 is the industrial-grade figure — it guarantees the breaker clears a 20 kA prospective fault at 400 VAC without welding or rupturing. For DC circuits it's rated 15 kA at up to 72 V. If your panel's available fault current sits between 10 and 20 kA, the 60947-2 rating is the one that governs the installation's SCCR.