What the ratings mean for fit
The Siemens SENTRON 3VA2340-6JQ32-0KA0 is a 3-pole molded case circuit breaker rated for line protection, with a continuous current of 400 A at 40 °C and an adjustable trip unit spanning 80 A to 400 A. That adjustable range means one breaker body covers feeder circuits from a 100 A branch up to the full 400 A main — the trip unit sets the actual protection threshold, not the breaker frame. Its interrupting capacity is 242 kA at 240 V, 187 kA at 415 V and 440 V, 121 kA at 500 V, and 7.5 kA at 690 V. At 480 V typical of North American industrial panels, the 187 kA at 440 V is the closest published figure — well above most service-entrance available fault currents. The sharp drop to 7.5 kA at 690 V means this breaker is sized for low-voltage distribution (≤ 600 V class), not 690 V motor circuits. Thermal derating is published: the breaker carries 400 A up to 50 °C, then steps down to 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C. In a warm panel near the top of a switchboard, that 70 °C ambient knocks capacity by 25 % — plan the load accordingly. The unit includes a shunt trip release (STL) for remote opening and a communication function for integration with a BMS or power monitoring system. Power loss is 96 W maximum — negligible for panel thermal design but worth noting if the breaker is enclosed in a small non-ventilated box.
Physical footprint and panel integration
Dimensions are 248 mm high, 138 mm wide, 110 mm deep. The 138 mm width (5.43 in) is standard for a 3-pole 400 A frame — it fits existing SENTRON 3VA panel cutouts and busbar riser spacing without re-drilling. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. The -25 °C lower operating limit suits unheated electrical rooms in cold climates, but the breaker should not be switched on below that temperature without warming the enclosure first.