Siemens 5SJ6250-7 SENTRON MCB — 50 A, 2-Pole, C-Curve
The Siemens 5SJ6250-7 is a 2-pole miniature circuit breaker from the SENTRON 5SJ6 series, rated 50 A at 400 V AC with a C-curve tripping characteristic. Its 6 kA breaking capacity per EN 60898 (and matching IEC 60947-2 rating) covers standard commercial and light industrial panelboard fault levels — enough for most distribution subfeeds where the upstream device provides the higher interrupting rating. The C-curve (5–10× In magnetic trip) handles moderate inrush from motor starters or capacitor banks without nuisance tripping, while still clearing low-impedance faults fast enough for basic cable protection.
What the ratings mean for fit
Rated 50 A continuous at 40 °C ambient — that is the load current the bimetal element carries without tripping. The C-curve means magnetic trip occurs between 5× and 10× In (250–500 A), so it coordinates downstream of a 63 A or 80 A upstream MCB without losing selectivity on moderate overloads. Maximum operating voltage is 440 V AC for multi-phase circuits; single-phase to neutral is limited by the 400 V line-to-line rating. The 6 kA breaking capacity is the maximum prospective fault current it can safely interrupt at the rated voltage — adequate for most sub-distribution boards fed by a transformer under 630 kVA, but verify against the available fault current at the panel. Terminals accept solid or stranded conductors from 0.75 mm² up to 25 mm² — sized for the 50 A rating (typically 10 mm² or 16 mm² copper). The sealable terminal covers allow the installer to lock the screws after torquing, which some site specs require for tamper-proofing. Installation depth is 70 mm, fitting standard SENTRON distribution boards and most DIN-rail enclosures with that clearance. The 2-module width (36 mm on a standard DIN rail) occupies two positions in the panel schedule.
Where it is used
This is a DIN-rail mounted MCB for final subcircuit protection in commercial and light industrial panelboards — lighting, socket outlets, small motor loads, and control transformers. The IP20 rating (with conductors connected) means it lives inside a closed enclosure, not in a wet or dusty environment. Ambient temperature range is -20 °C to +45 °C for normal operation, with storage from -40 °C to +75 °C. Vibration resistance to 50 m/s² at 25–150 Hz and 60 m/s² at 10–150 Hz per IEC 60068-2-6 makes it suitable for installation on machinery panels subject to moderate vibration.