What it is and what it does
The Siemens 5SJ4150-7HG40 is a 1-pole SENTRON miniature circuit breaker rated 50 A AC at 30 °C and 40 °C, with a 60 V DC maximum. Its 18 mm width fits one modular unit on standard DIN rail, making it a direct drop-in for panels built around the 5SJ4 family.
What the ratings mean for your panel
The 50 A rating holds at 30 °C and 40 °C ambient; at 45 °C it derates to 49 A, at 50 °C to 47.6 A, at 55 °C to 46.3 A, and at 60 °C to 45 A. That thermal curve matters when the breaker sits in a crowded enclosure — if your panel ambient hits 50 °C, plan for 47.6 A continuous, not the full 50 A. The 60 V DC maximum covers control-circuit protection but not typical 110 V DC or higher battery banks.