What it is and what it does
The Siemens 3VA2440-6HM32-0AA0 is a SENTRON molded case circuit breaker (MCCB) rated for 400 A continuous at 70 °C ambient — no derating needed up to that temperature, which is unusual for a breaker this size. It carries a 3-pole design with an ETU330 electronic overcurrent release, meaning the trip curve is adjustable and more precise than a thermal-magnetic unit. The interrupting ratings are what you'd expect from a serious feeder breaker: 242 kA at 240 V, 187 kA at 415 V and 440 V, 121 kA at 500 V, and 9 kA at 690 V. That 242 kA at 240 V tells you it's built for high-fault-current panels — likely a main or large feeder in an industrial distribution board.
Panel fit and integration
Footprint is 138 mm wide by 248 mm tall by 110 mm deep — that's about 5.43 by 9.76 by 4.33 inches. It's a standard MCCB form factor for a 400 A frame; you're not going to have trouble finding space on a DIN rail or in a panel cutout, but verify the mounting pattern against your existing busbar or lug kit. IP40 on the front means it's protected against solid objects over 1 mm — fine for a dry indoor panel, but not for washdown areas. Max power loss is 63.5 W, so factor that into your enclosure thermal budget if you're packing several breakers in a small cabinet.