What it is and what it does
The Siemens SENTRON 3VA2340-5KP32-0AC0 is a 3-pole molded case circuit breaker (MCCB) rated for 400 A continuous current at 40 °C, designed for line protection in distribution panels. It carries a 187 kA interrupting capacity at 240 V AC — that's the fault current it can safely clear without welding contacts or rupturing the case, which matters when you're coordinating downstream breakers on a high-capacity transformer secondary. The interrupting rating drops to 121 kA at 415 V and 440 V, 75.6 kA at 500 V, and 7.5 kA at 690 V, so verify your system voltage against the curve before specifying. This MCCB includes a communication function for remote monitoring and trip-event logging. The auxiliary switch design is listed as 2 auxiliary switches HQ.
Thermal derating and panel fit
The 400 A rating holds up to 50 °C ambient; above that, derate linearly to 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C. If your panel runs hot — say a packed enclosure near a furnace line — you need to account for that drop. The dimensions are 248 mm high, 138 mm wide, 110 mm deep, so it fits a standard MCCB footprint on a DIN rail or direct-mount plate. Max power loss is 96 W at full load, which adds to the enclosure's thermal budget.