Switch Disconnector for Isolation and Safety Switching
The Siemens SENTRON 3VA1112-1AA42-0CC0 is a 4-pole switch disconnector in MCCB design, rated for a continuous current of 125 A. It is built on the 3VA1 IEC frame 160 platform and is intended for isolation and safety disconnection of circuits where overload or short-circuit protection is handled by upstream devices. The unit includes an integrated undervoltage release (UVR) rated for 120-127 V AC at 50/60 Hz, which automatically opens the disconnector when control voltage drops, providing a standard method for emergency-off or interlock circuits per IEC 60947-2. With a rated insulation voltage of 800 V and maximum operational voltages of 690 V AC and 600 V DC, this disconnector is suited for 400 V and 480 V distribution panels as well as DC bus applications. The front-terminal busbar connection simplifies panel wiring, and the IP40 front protection is adequate for enclosed switchboard installation where the front face is behind a door.
Key Ratings and What They Mean for Fit
The 125 A rated continuous current (Iu) is the maximum current the disconnector can carry continuously without exceeding its thermal limits. For a 125 A feeder, this part provides a direct match; for lower-current circuits, it offers headroom but occupies the same panel space as a 125 A device. The 2 kA short-time withstand rating at both 0.5 s and 1 s confirms it can hold off fault currents up to that level during coordination with upstream breakers — this is the rating that governs selectivity in a distribution hierarchy, not the breaking capacity of a full MCCB. The 2 auxiliary switches (HQ type) provide two changeover contacts for status feedback to a PLC or indication lamp. The undervoltage release (UVR) is wired separately from the main circuit; its 120-127 V AC coil must be continuously energized for the disconnector to remain closed. This is a common configuration for safety circuits where loss of control voltage must open the main contacts.
Panel Integration Notes
The disconnector measures 130 mm high, 101.6 mm wide, and 70 mm deep (-). The 4-pole width occupies four module spaces on a DIN rail or mounting plate. The front-terminal busbar connection accepts busbar fingers or cable lugs; the busbar system must be rated for the 125 A continuous current. Operating temperature range is -25 °C to +70 °C, with storage from -40 °C to +80 °C. Maximum power loss is 38 W, which should be factored into enclosure thermal calculations.