The Siemens SENTRON 5SL6440-7 is a 4-pole miniature circuit breaker (MCB) with a C-tripping characteristic, rated 40 A at 400 V AC and a 6 kA breaking capacity per EN 60898 and IEC 60947-2. The 6 kA rating is the standard residential and light commercial fault level; for higher available fault currents you would step to the 10 kA or 15 kA variants in the same SENTRON family.
The 40 A rating is at 30 °C ambient; at 40 °C it derates to 38.07 A, and at 55 °C to 34.97 A — so in a warm enclosure you may need to step to a 50 A frame if the continuous load is near 40 A. Operating voltage is 400 V AC three-phase, with a maximum of 440 V AC in multi-phase operation.