What this MCCB is and where it lands
The Siemens 3VA2340-5JQ32-0HH0 is a SENTRON molded case circuit breaker (MCCB) sized for line protection in main distribution panels. Three poles, adjustable from 600 A to 4000 A, so it covers a wide range of feeder and main-breaker roles without swapping frames.
Breaking capacity — what the numbers mean for fault duty
Rated 187 kA at 240 V, 121 kA at 415 V and 440 V, 75.6 kA at 500 V, and 7.5 kA at 690 V. That 187 kA figure at 240 V tells you this breaker handles high available fault current on the low-voltage side of a step-down transformer without needing a current-limiting fuse upstream. At 690 V the rating drops to 7.5 kA — still adequate for most 690 V motor control centers, but verify the system fault level if you are close to the transformer secondary.
Thermal derating — the real continuous current
Rated 400 A continuous at 40 °C, 45 °C, and 50 °C. At 55 °C it derates to 375 A, at 60 °C to 350 A, at 65 °C to 325 A, and at 70 °C to 300 A. If your panel ambient runs above 50 °C, the 400 A frame still delivers but you need to account for the lower ampacity in the load schedule. The 96 W maximum power loss at full load matters for enclosure heat rise calculations — that is heat that stays inside the cabinet.
Integration — panel fit and auxiliaries
The 3VA2340-5JQ32-0HH0 measures 248 mm high, 138 mm wide, and 110 mm deep. That 110 mm depth is the dimension from the mounting surface to the farthest projection — useful when you are checking gland-plate clearance or door swing. It ships with 2 auxiliary switches plus 1 trip alarm switch (HQ configuration) and a shunt trip release (STL), so you get remote status and remote trip out of the box without ordering separate accessory kits. The undervoltage release is not fitted — if you need UVR protection, that is a field-add or order variant decision.