What it is and what the ratings mean
The Siemens 3VA1112-6MH36-0AE0 is a 3-pole IEC frame 160 molded case circuit breaker rated 125 A, with a breaking capacity of 70 kA at 415 V (class H). That Icu rating means it can safely interrupt a fault current up to 70,000 A without welding its contacts or rupturing the arc chamber — essential for high-fault installations like large motor control centers or transformer secondaries where available short-circuit current is substantial. The TM120M trip unit is thermal-magnetic: the thermal element handles overload protection (inverse-time curve), while the magnetic element provides short-circuit protection with an adjustable instantaneous pickup range of 5 to 15 times In (625 A to 1875 A). Note that this variant ships without overload protection — the TM120M provides only short-circuit protection, so an external overload relay is required for motor starting duty.
Deployment context and integration
Mounts in a standard panel on a DIN rail or fixed baseplate. The clamp-type terminals accept copper or aluminum conductors up to the frame's rated cross-section — no lug kit needed for most wiring. Four auxiliary switches (2 NO + 2 NC) are built in, giving status feedback to a PLC or indicating lamp without adding external contact blocks. Rated for 50/60 Hz distribution systems. The 125 A continuous rating suits it for feeder protection in sub-distribution boards, backup generator outputs, or as a main disconnect for a machine cell drawing under 125 A full load.