The Siemens SENTRON 3VA1112-1AA36-0CC0 is a 3-pole switch disconnector in MCCB design, rated for 125 A continuous current (Iu) with a max operational voltage of 690 V AC and 500 V DC. It's built on the 3VA1 frame (160 A frame size) and comes configured as an SD100 — meaning it provides isolation and switching but no overload or short-circuit protection. That makes it a pure disconnect for a panel feeder or branch circuit where upstream protection already exists. It ships with an undervoltage release (UVR) rated for 120-127 V AC 50/60 Hz, plus two HQ auxiliary switches (form C, 2 CO contacts). The UVR will trip the disconnect if control voltage drops below the dropout threshold — common in safety circuits or emergency-stop chains where loss of control power must open the main contacts.
What the ratings mean for fit
The 125 A rated continuous current (Iu) is the steady-state load this disconnect can carry without exceeding its thermal limits. For motor loads, you'd size it to the motor FLA plus any continuous auxiliary loads — 125 A covers a 55 kW motor at 400 V (roughly 104 A FLA) with headroom. The 690 V AC rating means it's suitable for 400 V and 480 V distribution panels; the 500 V DC rating opens it for DC bus or battery-bank isolation. The 2 kA limited short-time withstand (1 s and 0.5 s) tells you this disconnect can survive a fault current up to 2 kA for those durations while the upstream breaker clears. That's a modest rating — it's not a high-fault device. It expects to be fed from a breaker or fuse with a lower let-through, typical in secondary distribution or sub-panel applications. IP40 on the front means it's protected against tools and wires >1 mm but not against water ingress — standard for indoor panel mounting where the enclosure door provides the environmental seal. The 38 W maximum power loss at rated current matters for thermal management inside a sealed cabinet; factor it into your panel cooling budget.
Panel integration notes
Dimensions: 130 mm height, 76.2 mm width, 70 mm depth. The 76.2 mm width is a standard 3-pole MCCB footprint (roughly 3 x 25.4 mm per pole) — it fits most DIN-rail or direct-panel mounting patterns for 160 A frame disconnects. Front terminals accept lug or clamp connections; the terminal arrangement is front-accessed for bus-bar or cable entry. The UVR coil draws from the control circuit — verify your 120-127 V AC supply can source the inrush without dropping below the release threshold. The two HQ auxiliary switches are wired via the front terminal block; they change state with the main contacts, giving you status feedback to a PLC or indicator lamp.