The Siemens SENTRON 5SJ4105-8HG42 is a 1-pole miniature circuit breaker (MCB) with a D tripping characteristic, rated 0.5 A at AC and 10 kA breaking capacity per EN 60898.
At 30 °C and 40 °C the breaker holds a full 0.5 A. Above that, it derates linearly: 0.48 A at 45 °C, 0.46 A at 50 °C, 0.44 A at 55 °C, and 0.42 A at 60 °C. If your panel ambient runs 50 °C — common in a sealed cabinet with drives — you have 0.46 A of headroom, not 0.5 A. That derating curve is the real selection number, not the label.
DC rating and application fit
The DC side is rated 60 V maximum. That covers 24 VDC control circuits and 48 VDC signal loops, but not a 110 VDC battery bank. For DC applications, the D curve's magnetic trip threshold (10–20× In) means it will hold through a capacitor bank charge cycle, but verify the DC voltage does not exceed 60 V.