The Siemens SENTRON 3VA1050-4ED36-0CH0 is a 3-pole molded case circuit breaker (MCCB) rated for line protection, carrying a continuous current Iu of 50 A up to 40 °C and derating to 45 A at 70 °C. The 121 kA breaking capacity at 240 V is the headline figure for high-fault panels; at 415 V it still holds 75.6 kA, and at 690 V it drops to 11.9 kA — so the SCCR you need for your transformer secondary or bus tie determines the voltage you spec against.
The 50 A frame is thermally rated — it holds 50 A continuously at 40, 45, and 50 °C ambient, then steps down to 48 A at 55 °C, 47 A at 60 °C, 46 A at 65 °C, and 45 A at 70 °C.
Integrated undervoltage release and auxiliary contacts
The latching endurance is rated at 15 000 operations — mechanical life for the mechanism, not the electrical breaking count.