What this part is and what it does
The Siemens SENTRON 3VA1112-1AA42-0KH0 is a 4-pole switch disconnector in MCCB design — it provides visible isolation and manual switching for a circuit but carries no overload or short-circuit protection (the 'SD100' designation means it's a straight disconnector only). Rated continuous current Iu is 125 A, with max operational voltage 690 V AC 50/60 Hz and 600 V DC. That makes it suitable for isolating a 125 A feeder in a 400 V or 480 V distribution panel, or a DC bus up to 600 V. The main circuit connects via busbar connection with front terminals — it's designed to bolt directly onto a busbar stack in a panel, not for cable lugging. IP40 on the front face keeps dust out of the enclosure front. It ships with a shunt trip release (STL) rated 220-250 V DC / 208-277 V AC, plus 2 auxiliary switches HQ and 1 trip alarm switch HQ. That means you can remote-trip it from a PLC or E-stop circuit and get status feedback on the switch position and whether it tripped via the shunt.
Sourcing and lifecycle
This is a standard catalog item from the SENTRON 3VA family, widely specified in IEC distribution boards. Sourced and quoted to order against an RFQ through independent distribution; availability and current pricing confirmed at quote time.
What the ratings mean for fit
At 125 A continuous, this switch disconnector handles the full rated current of a 125 A feeder without derating — no thermal trip curve to worry about since there's no overcurrent release. The 15 000 latching endurance cycles (mechanical life) is typical for a disconnector in this frame size; it's not a daily-switch duty part but fine for infrequent isolation or maintenance switching. The 2 kA limited short-time rating (1 s and 0.5 s) tells you it can withstand a fault current up to 2 kA for those durations without welding contacts — important for coordination with an upstream protective device. Below that threshold it's a safe isolation point; above it you need the upstream breaker to clear before the disconnector fails. Power loss is max 38 W at rated current. That's heat that needs to be considered in a sealed enclosure — 38 W per unit adds up in a multi-feeder panel, so account for ventilation or derating if ambient hits 70 °C (the max operating temp). Dimensions are 130 mm height, 101.6 mm width, 70 mm depth — the 101.6 mm width is a standard 4-pole MCCB footprint (roughly 4 x 25.4 mm per pole). It will fit the same busbar mounting pattern as other 3VA1 frame 160 disconnectors.