The Siemens 3VM9908-0BB11 is a SENTRON undervoltage release rated for 24V DC, designed as an auxiliary release accessory for 3VM circuit breakers up to 630A. It drops the breaker when control voltage falls below the dropout threshold — a standard requirement for emergency-stop circuits and undervoltage protection schemes in industrial panels.
The 4 kV surge voltage resistance covers transient overvoltages from the mains side, so the release won't nuisance-trip or fail on a nearby lightning strike or switching surge. Power consumption is 2.5 W max at DC — a modest continuous draw that a 24V DC supply can handle without derating, but worth budgeting if you're stacking multiple releases on the same control transformer. Physical footprint: 28.8 mm deep × 25.7 mm wide × 65.1 mm high. That compact width lets it snap into the accessory slot on the 3VM breaker without expanding the DIN-rail footprint. The 10 mm stripped length matches standard ferrule preparation for the control wiring.
Integration note
Mounts directly into the accessory slot on 3VM breakers up to 630A frame. No additional DIN-rail space required — the release sits within the breaker envelope. Confirm polarity on the DC supply and verify free-wheel diode suppression if the release shares a control transformer with inductive loads.