Siemens 3VA1112-6MH36-0JH0 — SENTRON MCCB for Motor and Starter Protection
The Siemens 3VA1112-6MH36-0JH0 is a SENTRON molded case circuit breaker (MCCB) designed specifically for starter protection, meaning it coordinates with contactors and overload relays to clear faults before they damage downstream motor-starting components. Rated 125 A continuous at 40 °C, it carries the full motor FLA for a 75–100 kW induction motor on 400 V three-phase, depending on duty cycle. The 3-pole frame with a shunt trip (STL) release and two auxiliary switches plus one trip alarm switch gives the panel builder both remote trip capability and status feedback to a PLC or safety relay. Breaking capacity is the headline number for this class: 220 kA at 240 V, 154 kA at 415 V, and 75.6 kA at 440 V. At 690 V it still holds 7.5 kA. For a panel fed from a 2 MVA transformer or a large genset, that 220 kA at 240 V means the MCCB can interrupt a full bolted fault without upstream fuses needing to clear — it self-protects. The 800 V rated insulation voltage confirms it is rated for 690 V line-to-line systems common in heavy industrial drives.
Integration — Panel Fit and Wiring
The 3VA1112 frame measures 130 mm high, 76.2 mm wide, and 70 mm deep. It mounts on a DIN rail or directly to a backplate via the screw terminals. The 70 mm depth is shallow enough for a 200 mm deep enclosure; the 76.2 mm width (3 inches) matches the standard 3-pole MCCB footprint, so it drops into existing busbar or cable-lug layouts without panel rework. The shunt trip release requires a separate control voltage — verify polarity and suppression per the wiring diagram before energizing.
Thermal Derating — Continuous Current vs. Ambient
Continuous current rating holds at 125 A from 40 °C through 50 °C, then derates linearly: 122 A at 55 °C, 120 A at 60 °C, 117 A at 65 °C, and 114 A at 70 °C. In a sealed panel with internal heat rise, the 55 °C row is the realistic design point — plan for 122 A continuous if the enclosure ambient hits that level. Maximum power loss at rated load is 28.1 W, which matters for thermal management in a multi-breaker lineup.