What it is and what it does
The Siemens SENTRON 3VA1112-4EF32-0JC0 is a 3-pole molded case circuit breaker (MCCB) designed for line protection in distribution panels and industrial switchboards. It carries a continuous current rating of 125 A at 40 °C, with a rated insulation voltage of 800 V. The breaker's interrupting capacity reaches 121 kA at 240 V and 75.6 kA at 415 V, which gives you headroom for high-fault installations like substation feeders or large motor control centers.
Current derating — what the thermal curve means for your panel
The 125 A rating holds flat from 40 °C through 50 °C, then begins a gradual decline: 122 A at 55 °C, 120 A at 60 °C, 117 A at 65 °C, and 114 A at 70 °C. If your enclosure runs hot — say a non-ventilated panel next to a furnace line or a packed cabinet with multiple breakers — you need to size for the derated figure, not the 125 A nameplate. The 28.1 W maximum power loss also contributes to internal heat rise, so factor that into your thermal budget.
Breaking capacity across voltage levels
This breaker delivers 121 kA at 240 V, 75.6 kA at 415 V, 52.5 kA at 440 V, and 11.9 kA at both 500 V and 690 V. The steep drop above 500 V is typical for MCCBs with this frame size — the arc extinction physics limit the interruption at higher line voltages. For 690 V applications, verify that 11.9 kA exceeds your available fault current; if it doesn't, you need a current-limiting upstream device or a higher-rated frame.
Built-in auxiliary components
Factory-fitted with 2 auxiliary switches (HQ type) and a shunt trip release (STL). The auxiliary switches give you remote status feedback — open/closed indication to a PLC or status lamp. The shunt trip allows remote tripping from an E-stop button or a safety relay, which is common in emergency-off circuits. No undervoltage release or ground-fault monitoring on this variant.
Physical fit — panel integration note
Dimensions: 130 mm height, 76.2 mm width (3 in), 70 mm depth. The 3-pole width is standard for a 125 A frame — it fits a 3-module DIN-rail slot or a bolted panel-mount footprint. Depth of 70 mm means it clears most 200 mm deep enclosures with room for wiring gutters. The 70 °C maximum operating temperature and -25 °C minimum cover most indoor industrial environments; storage range from -40 °C to 80 °C handles warehouse extremes.