What this MCCB delivers — and what the ratings mean for your panel
The Siemens 3VA2340-5JQ32-0AF0 is a SENTRON molded case circuit breaker (MCCB) rated 400 A continuous at 40 °C, with a maximum interrupting capacity of 187 kA at 240 V AC. That 187 kA figure means it can safely clear a fault current up to that level without welding contacts or rupturing the case — critical for high-fault installations like transformer secondaries or large motor control centers. At 415 V it still holds 121 kA, and at 690 V it drops to 7.5 kA, so the voltage-dependent curve governs where you place it in the distribution. Three poles, line-protection design (not motor-protection), with a built-in communication function for remote monitoring or trip-event capture. The auxiliary switch configuration is 1 auxiliary switch plus 1 trip alarm switch HQ — enough for a remote status and a separate alarm signal back to the PLC or SCADA.
Thermal derating — the real-world current you can actually carry
Rated 400 A from 40 °C through 50 °C ambient. Above that it derates: 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 non-ventilated enclosure near a furnace line — that 70 °C figure is the one to design to, not the catalog 400 A. The maximum power loss at rated load is 96 W, so factor that into your enclosure heat budget.
Footprint and panel integration
Dimensions: 248 mm high, 138 mm wide, 110 mm deep. That 110 mm depth means it fits standard 200 mm deep enclosures without crowding the gland plate. The 138 mm width is a three-pole frame — check your busbar spacing if you're retrofitting into an existing panel that was laid out for a narrower frame.