The Siemens 3VA1112-5MH32-0KA0 is an IEC frame 160 molded-case circuit breaker with a 125 A rating and a 55 kA interrupting capacity at 415 V AC (breaking capacity class M). It's a 3-pole unit designed for starter protection — meaning it sits upstream of a motor starter to handle short-circuit faults, not overloads. The TM120M thermal-magnetic trip unit is set for magnetic-only (short-circuit) protection with an adjustable instantaneous pickup between 5 and 15 times In, so you dial it in to coordinate with the starter's contactor and OL relay. The integrated shunt trip (STL) operates on 220-250 V DC or 208-277 V AC, letting you remotely trip the breaker from an E-stop or safety PLC.
What the ratings mean for fit
The 55 kA Icu at 415 V indicates the breaker can clear a fault up to that level without welding contacts. The 125 A continuous rating matches a typical motor load, but the adjustable instantaneous trip (5–15× In) is the key selection parameter.
Mounting and integration
Mounts on a standard DIN rail or directly to a panel backplate via the four mounting slots on the breaker base. The nut keeper kit (included per the order code) secures the line and load lugs — no lost hardware during panel build-out. The shunt trip terminals are clearly marked and accept 1.5–2.5 mm² wire; strip length 8 mm for cage clamps. Plan for a minimum 10 cm clearance above and below the breaker for arc-vent path and cable bending radius.