What this MCCB is and what it does
The Siemens SENTRON 3VA1112-3EF32-0CA0 is a 3-pole molded case circuit breaker (MCCB) designed for line protection in distribution panels and switchgear. It carries a continuous current rating of 125 A at 40 °C, with a TM240 thermal-magnetic overcurrent release — the '240' indicates the fixed thermal trip threshold in amperes, so this unit is sized for 125 A continuous but the release element is calibrated for a 240 A frame. The breaker includes an undervoltage release (UVR) as the auxiliary release, meaning the trip coil will open the breaker if the control voltage drops below a set threshold — a common requirement for emergency-stop circuits and mains disconnection schemes. Rated insulation voltage is 800 V, and the breaking capacity varies by system voltage: 75.6 kA at 240 V, 52.5 kA at 415 V, 32 kA at 440 V, and 11.9 kA at both 500 V and 690 V. These figures give the SCCR (short-circuit current rating) the breaker can safely interrupt at each voltage level — critical for selectivity studies and panel SCCR labeling per UL 508A or IEC 61439.
Thermal derating and operating envelope
The 125 A rating holds from 40 °C through 50 °C. Above that, the continuous current must be derated: 122 A at 55 °C, 120 A at 60 °C, 117 A at 65 °C, and 114 A at 70 °C. If this breaker sits in a high-ambient panel (near a drive or transformer), the 70 °C limit of 114 A is the number to use for the BOM line — not the catalog 125 A. Operating temperature range is -25 °C to +70 °C; storage range is -40 °C to +80 °C. Maximum power loss is 30.6 W — a relevant figure for enclosure thermal calculations, especially in sealed or high-fill-factor panels where heat buildup accelerates derating.
Panel fit and mounting
Dimensions are 130 mm height, 76.2 mm width, and 70 mm depth. The 70 mm depth is the dimension from the mounting surface to the front of the breaker — relevant when planning gland-plate clearance or door-mounted operator depth. Width of 76.2 mm (3 inches) is standard for a 3-pole MCCB in this frame class, so it fits existing DIN-rail or panel-mount footprints without re-drilling. No communication function or ground-fault monitoring is built in; this is a standalone thermal-magnetic breaker with undervoltage release only.