What It Is and What It Does
The Siemens 3VA1112-1AA42-0DD0 is a 4-pole switch disconnector from the 3VA1 IEC frame 160 series, rated at In=125A. It provides visible isolation for a circuit but carries no overload or short-circuit protection — it is a disconnect switch, not a breaker. The integrated undervoltage release (208-230V AC 50/60Hz) automatically opens the switch when control voltage drops, protecting downstream equipment from brownout or phase-loss conditions. Three auxiliary switches (HQ type) report the main contact position back to a PLC or status panel.
Deployment Context
Mounts on a DIN rail inside a standard IEC enclosure. The 4-pole configuration suits three-phase plus neutral disconnection for motor feeder or distribution sub-circuits. The undervoltage release coil draws continuously when energized — factor that into control transformer sizing.