The Siemens 3VA1112-5MH32-0KC0 is a SENTRON molded case circuit breaker built for starter protection — meaning it's sized to sit ahead of a motor starter, not just a feeder breaker. Rated 125 A continuous at 40 °C and holding that same 125 A all the way up to 50 °C, it's got thermal headroom for warm enclosures. The 3-pole design and a shunt trip release (STL) let you drop the breaker remotely, which is handy for emergency-stop circuits or controlled shutdowns on a conveyor line.
Breaking capacity — what it handles
This MCCB can interrupt 187 kA at 240 V, 121 kA at 415 V, and 75.6 kA at 440 V. That's a serious fault-current rating — it'll clear a bolted short without welding its contacts shut, which is what you need when the transformer feeding the panel can dump that kind of energy. At 500 V and 690 V the rating drops to 7.5 kA, so if you're running at those voltages, make sure the available fault current stays under that number.
Fit and mounting
The 3VA1112-5MH32-0KC0 measures 70 mm deep, 76.2 mm wide, and 130 mm tall. That 76.2 mm (3-inch) width is the standard 3-pole MCCB footprint for this SENTRON family — it'll drop into the same DIN-rail or panel-mount slot as other 3VA breakers. The depth of 70 mm means it doesn't stick far into the enclosure, leaving room for wiring gutters or a second row of breakers behind the door.
Thermal derating and ambient range
From 40 °C to 50 °C the breaker holds a flat 125 A. At 55 °C it derates to 122 A, at 60 °C to 120 A, at 65 °C to 117 A, and at 70 °C to 114 A. The operating ambient range is -25 °C to 70 °C, with storage from -40 °C to 80 °C. That's a solid thermal envelope for a motor-control center in a hot plant — no need to oversize just because the panel sits near a furnace or in a sun-baked electrical room.
Auxiliary switch and shunt trip
The breaker ships with two HQ auxiliary switches and a shunt trip (STL) release. The shunt trip lets you trip the breaker from a remote pushbutton or a safety relay — common for E-stop circuits or PLC-driven shutdown sequences. The two auxiliary switches give you status feedback (open/closed) back to the controller or a panel lamp. No undervoltage release is fitted, so the breaker won't drop out on a brownout unless you add one separately.
Power loss and insulation
Maximum power loss is 28.1 W at rated current. The rated insulation voltage is 800 V.