What it is and what it does
The Siemens SENTRON 3VA2125-7MS32-0AA0 is a 3-pole molded case circuit breaker (MCCB) rated for 25 A continuous current, with an adjustable overload and short-circuit trip range from 75 A minimum to 375 A maximum. It uses the ETU310M electronic trip unit, which is a microprocessor-based release designed for motor and starter protection — the 'M' in the designation stands for motor protection, meaning the trip curve is shaped to handle inrush without nuisance tripping while still providing fast fault clearing. This MCCB sits in the SENTRON family, Siemens' standard line for distribution and motor branch circuits in industrial panels. The 3VA platform replaced the older 3VL series and is current-production, so it's what you'll get on a new BOM or as a like-for-like replacement in an existing SENTRON panel.
Interrupting capacity — what the numbers mean for your panel
The interrupting capacity is the breaker's ability to safely clear a fault without welding contacts or rupturing the case. At 240 V AC this breaker handles 330 kA — that's extremely high, typical for a feeder breaker close to a large transformer or in a high-fault-current industrial service entrance. At 415 V and 440 V it's still 242 kA, dropping to 187 kA at 500 V, and 3.7 kA at 690 V. The steep drop at 690 V reflects the arc-extinction limits of air at that voltage; this breaker is primarily designed for 240–500 V systems, not 690 V motor circuits.
Thermal performance and environment
The 25 A continuous rating holds flat from 40 °C up to 70 °C ambient — no derating needed in a warm panel. Operating range is -25 °C to 70 °C, storage from -40 °C to 80 °C. Rated insulation voltage is 800 V, which covers most 480/277 V and 600 V systems with margin. Maximum power loss is 0.6 W, negligible for panel thermal budgeting.
Physical fit and mounting
Dimensions: 105 mm wide, 181 mm tall, 86 mm deep. That's a standard 3-pole MCCB footprint for this current class — mounts on a DIN rail or directly to a backplate via the screw terminals. The 86 mm depth includes the arc chamber and line/load lugs; make sure your enclosure has at least 100 mm clearance in front for wiring and arc flash boundary.