Siemens Betagard 5SL4125-0RC is a 1-pole miniature circuit breaker rated 25 A at AC with a Z tripping characteristic and a 10 kA breaking capacity per EN 60898. Z curve trips fast on low-level overcurrents — it's meant for semiconductor or sensitive electronic loads where standard B/C curves would let too much energy through before opening. Snaps onto DIN rail, takes 1 modular width (18 mm), and can mount in any position.
Temperature derating and voltage limits
At 30 °C ambient the breaker carries 28 A; at 40 °C it's 26.5 A; at 50 °C it's back to 25 A; at 60 °C it's 23.4 A. Single-phase AC rating is 440 V; multi-phase AC rating is also 440 V. DC rating maxes at 72 V — so for a 48 VDC control bus it's fine, but not for a 125 VDC battery string.
IP20 with connected conductors — protected against finger touch but not water ingress. Pollution degree 2, overvoltage category III, vibration resistance 50 m/s² at 25 to 150 Hz per IEC 60068-2-6. Halogen-free and silicon-free, sealable, touch-protected terminals. Fits standard 18 mm DIN-rail slot.