The Siemens SENTRON 3VA1340-4EF32-0DH0 is a 3-pole molded case circuit breaker rated 400 A at 40 °C, with a breaking capacity of 121 kA at 240 V AC. At 415 V it still holds 75.6 kA, and at 690 V it's 11.9 kA, so the SCCR headroom drops fast as voltage climbs; verify your point-of-fault voltage before assuming the top number applies.
The TM240 overcurrent release is a thermal-magnetic type — thermal element handles overloads (slow trip, inverse-time curve), magnetic element handles short-circuits (instantaneous). The '240' in TM240 refers to the frame size or release rating, not the amp rating; the actual continuous current is 400 A at 40 °C ambient. That 400 A holds steady up to 50 °C, then derates to 392 A at 55 °C and 367 A at 70 °C. That means if control voltage drops below the dropout threshold, the breaker trips instantly. Useful for emergency-stop circuits or undervoltage protection on motor feeders, but it also means a momentary brownout on the control bus will drop the main. The width is 138 mm for a 3-pole unit; a 4-pole version would be wider. Mounting is standard for SENTRON 3VA frames, so it fits the same panel cutouts and busbar adapters as other breakers in this family.