The Siemens SENTRON 3VA2340-6JQ32-0CH0 is a 3-pole molded case circuit breaker rated for 400 A continuous current (Iu) across ambient temperatures up to 50 °C, derating to 300 A at 70 °C. The interrupting capacity hits 242 kA at 240 V, 187 kA at 415/440 V, and still 40 kA at 690 V, which means it can handle high-fault scenarios downstream of large transformers or in industrial mains distribution without needing a current-limiting upstream device.
The 138 mm width for a 3-pole 400 A frame is typical for SENTRON 3VA2 breakers; verify the existing panel cutout if replacing a different manufacturer's 400 A frame, as the mounting hole pattern may differ.
Thermal management — 98.5 W max power loss
At full rated current, the breaker dissipates up to 98.5 W. In a sealed or tightly packed enclosure, that heat needs to be considered for the internal temperature rise — especially since the breaker itself derates above 55 °C. For a panel running at 40 °C ambient, the 400 A rating is safe; if the enclosure internal ambient hits 60 °C, you're down to 350 A.