630 A MCCB with 242 kA interrupt rating — what that means for your bus
The Siemens 3VA2463-6HN32-0KA0 is a SENTRON molded case circuit breaker rated 630 A continuous and 242 kA breaking capacity at 240 V — that interrupt rating means it can safely clear a fault up to 242,000 A without welding contacts or venting arc gas into the enclosure, which is the figure that governs whether it holds under a high-capacity transformer secondary. At 415 V the breaking capacity is still 187 kA, and at 690 V it drops to 9 kA, so the voltage-dependent curve determines where this breaker lands on your fault-current study. It is a 3-pole line-protection design with a shunt trip release (STL) built in, no undervoltage release, no ground-fault monitoring, and no auxiliary switch — it is a straight power breaker, not a multifunction device.
Thermal derating — the real current you can pull at panel ambient
The 630 A rating holds at 40 °C ambient. At 50 °C it derates to 593 A, at 60 °C to 557 A, and at 70 °C to 520 A — so if this breaker sits in a crowded panel with a 55 °C internal ambient, you are limited to 575 A continuous. The maximum power loss at rated current is 162 W, which must be dissipated inside the enclosure; that heat load factors into the panel cooling budget. Dimensions are 248 mm height, 138 mm width, 110 mm depth — the 138 mm width on a 3-pole frame means it occupies three 45 mm modular spaces on a DIN rail, standard for this class.