125 A MCCB with starter protection — what the ratings mean for fit
The Siemens SENTRON 3VA1112-5MH32-0DA0 is a 3-pole molded case circuit breaker (MCCB) designed specifically for starter protection — meaning it's tuned to handle motor inrush without nuisance tripping, while still clearing faults fast enough to protect the contactor and overload relay downstream. Rated 125 A continuously at 40 °C ambient, it holds that full rating 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 (–). That thermal curve matters when the breaker lives in a crowded panel — if your enclosure ambient runs 55 °C, the usable continuous current is 122 A, not 125 A. Breaking capacity is the headline number here. At 240 V AC it clears 187 kA; at 415 V it's 121 kA; at 440 V it drops to 75.6 kA; and at 500 V and 690 V it holds at 7.5 kA. That 187 kA at 240 V is exceptional — it means this breaker can be installed at the main distribution point with a high available fault current, not just downstream. For motor control centers on 400 V class systems, the 121 kA at 415 V gives real selectivity headroom against upstream devices. The overcurrent release is a TM120M — a thermal-magnetic unit with fixed thermal and magnetic settings matched to the 125 A frame. The design includes an undervoltage release (UVR) as standard, which automatically opens the breaker when control voltage drops below a threshold — a common requirement for safety circuits and emergency-stop chains. No ground-fault monitoring, no communication function, no voltage trigger. This is a straightforward, hardened protection device for motor circuits.
Lifecycle and sourcing reality
Rated insulation voltage is 800 V, which covers 480/600 V systems with margin. Power loss at rated load is 30.6 W maximum — relevant for thermal coordination in sealed enclosures. Storage temperature range is -40 to 80 °C; operating range is -25 to 70 °C. Mounts on a standard DIN rail or panel-mount via the 70 mm depth, 76.2 mm width, 130 mm height footprint (–).
Panel integration — what fits where
The 3VA1112-5MH32-0DA0 occupies a 76.2 mm wide by 130 mm tall footprint with 70 mm depth behind the panel (–). That's a standard 3-pole MCCB envelope — it drops into the same cutout as other 125 A frame SENTRON breakers. The undervoltage release adds a pair of control wires; verify the coil voltage matches your control circuit before terminating. No auxiliary contacts are included on this variant — if you need alarm or position feedback, order the accessory kit separately.