What this MCCB is and what it does
The Siemens 3VA1112-3EF36-0BA0 is a SENTRON molded case circuit breaker (MCCB) for line protection in distribution panels. It carries a rated continuous current Iu of 125 A across three poles, with a TM240 thermal-magnetic release that handles overloads and short circuits without an external trip unit. The 125 A rating holds flat from 40 °C through 50 °C — no derating needed in a warm enclosure — then drops gradually to 112.5 A at 70 °C ambient. That thermal curve matters when you're packing breakers into a crowded panel and need to know the real ampacity at operating temperature.
Breaking capacity — what the numbers mean for coordination
This MCCB delivers 75.6 kA at 240 V, 52.5 kA at 415 V, 32 kA at 440 V, and 10.5 kA at 690 V. Those are the interrupting ratings at each voltage level — the fault current it can safely clear without welding contacts or rupturing the case. For a 415 V industrial feeder, 52.5 kA gives headroom above typical transformer fault levels (usually 25–40 kA), so you can coordinate downstream without cascading. At 690 V the 10.5 kA figure is lower, which is typical for a 125 A frame on higher voltage — check the available fault current at your secondary before committing this breaker to a 690 V bus.
Built-in undervoltage release — no auxiliary contacts
The 3VA1112-3EF36-0BA0 ships with an undervoltage release (UVR) as the integrated auxiliary release, part number 3VA9608-0BB11 for the trip coil assembly. That UVR will trip the breaker if the control voltage drops below its dropout threshold — useful for emergency-stop circuits or undervoltage protection on motor feeders. There is no separate auxiliary contact version on this variant, and no communication module or ground-fault monitoring. If you need remote status feedback, you'll add an external auxiliary switch block. The front face carries IP40 protection, so it's fine in a clean indoor panel but not for washdown environments.