Interrupting capacity and tripping curve — the two numbers that decide the BOM fit
The 5SJ4204-8HG42 carries a 10 kA interrupting rating per EN 60898 and a 15 kA rating per IEC 60947-2 — the higher figure applies when the breaker is part of an industrial panel where the prospective fault current at the bus can exceed 10 kA. The D-curve characteristic (10–20× In magnetic trip) means it tolerates the inrush of motor loads, solenoid banks, or transformers without nuisance tripping on start-up, while still clearing a bolted fault in under 10 ms. Rated 4 A at 400 VAC (50 Hz) and 60 VDC, the 2-pole design switches both line conductors simultaneously — no neutral switching. The 400 VAC rating covers line-to-line loads in three-phase panels; the 60 VDC rating limits it to low-voltage DC control circuits, not string-level solar or battery banks.
Depth is 70 mm including the handle overhang; the body is 121 mm tall. Combined (screw + cage) terminals top and bottom accept Cu conductors at 3.5 Nm tightening torque. The breaker is sealable, halogen-free, and silicon-free, which matters in clean-room or coated-board environments where outgassing can cause relay contact failure. Pollution degree 3, overvoltage category III, and IP20 (IP40 in the handle area) mean it is rated for the conductive-dust and condensation environment typical of industrial enclosures.
The 5SJ4 series is the SENTRON miniature circuit-breaker family for mechanical engineering and industry applications.