The Siemens SENTRON 3VA2340-6JQ32-0AA0 is a 3-pole molded case circuit breaker (MCCB) rated for 400 A continuous current at 40 °C, with an adjustable thermal-magnetic trip range from 600 A to 4 000 A — meaning you set the instantaneous pickup to match your feeder or main breaker coordination study, not a fixed threshold. Breaking capacity is 242 kA at 240 VAC, 187 kA at 415 V and 440 V, 121 kA at 500 V, and 7.5 kA at 690 V — so at typical 480 V distribution levels it clears fault currents well above what most service-entrance gear can deliver, and the 690 V rating covers 600 V class systems with a comfortable margin. It includes a communication function (likely PROFIBUS or PROFINET via a plug-in module) and summation-current ground-fault monitoring on the line conductors — useful for a main breaker that needs to report status and trip events to a BMS or SCADA system.
The breaker carries 400 A continuously up to 50 °C ambient, then derates to 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C — so in a hot switchroom or a panel with dense heat sources, expect to downrate the main bus by 25% at the upper end. Maximum power loss is 96 W at rated current — a modest figure for a 400 A frame, but enough to factor into enclosure ventilation if the breaker is in a sealed cabinet with other heat sources.
The 138 mm width is the same as the 3VA2 frame family, so if you are replacing a 3VA2225-5JQ32-0AK0 (225 A frame) with this 400 A unit, the panel cutout and busbar spacing are identical — no rewiring or re-drilling needed.