What it is and what it does
The Siemens 3VA1112-6MH36-0AG0 is a 3-pole IEC frame 160 molded case circuit breaker (MCCB) from the 3VA1 series, rated at 125 A with a breaking capacity of 70 kA at 415 V (class H). It is a starter-protection variant with a TM120M thermal-magnetic trip unit, set for motor starting duty without overload protection — meaning the thermal element is bypassed and only the magnetic short-circuit protection is active, adjustable between 5 and 15 times the rated current (Ii=5…15 x In). This makes it a magnetic-only breaker for motor short-circuit protection where overload protection is handled separately by a contactor/overload relay combination.
What the key ratings mean for fit
The 70 kA Icu at 415 V (breaking capacity class H) means this breaker can safely interrupt a fault current up to 70,000 A without damage — essential for high-fault-capacity installations like large motor control centers or transformer-fed panels. The magnetic-only trip (Ii=5…15 x In) means it will hold through motor inrush without nuisance tripping, but it will NOT provide overload protection; pair it with a properly sized overload relay on the contactor. The clamp connection accepts copper or aluminum conductors without lug kits, saving panel space and install time.
Where it lives in the panel
Mounts on a standard DIN rail or panel-mount via the 3VA1 fixed-base system. The 3-pole, 125 A frame fits in a standard MCCB footprint; plan for at least 75 mm of width per pole plus clearance for the auxiliary switch and trip alarm switch wiring. The integrated auxiliary switch (HP) and trip alarm switch (HP) provide status feedback to a PLC or indication lamp without needing add-on modules.