DC-rated MCB for 880 V strings
The Siemens 5SY5440-7CC is a SENTRON 5SY5CC series miniature circuit breaker rated for 880 V DC with a 10 kA breaking capacity per IEC 60947-2. Four poles, C-curve tripping at 40 A. The DC voltage rating is the headline here — most panel-mount MCBs top out around 250 V DC, so this one handles series-connected PV strings or battery banks where you need a single breaker instead of stacking poles.
The 4-pole configuration with no neutral switching tells you it's a DC ungrounded system breaker: all four poles in series for the DC rail, not a three-phase-plus-neutral AC layout. Terminal range 0.75…35 mm² solid or stranded covers everything from control-circuit tails to main feeder cable — no adapter lug needed up to 35 mm². Mounting position any, which simplifies panel layout when the busbar orientation forces a rotated breaker.
Width is 72 mm — that's 4 width units on a standard 18 mm/module rail. Combined terminals top and bottom let you feed through or daisy-chain without extra distribution blocks. Screw terminals torque to 2.5…3.5 N·m. Ambient -25…+55 °C operating, storage -40…+75 °C.