MCCB for motor branch circuits — interrupting capacity and thermal derating
The Siemens SENTRON 3VA2450-5MN32-0JH0 is a 3-pole molded case circuit breaker (MCCB) configured for motor protection, carrying a rated continuous current Iu of 500 A. It uses the ETU350M electronic overcurrent release with phase failure detection, making it suitable for protecting motor feeders where a tripping curve matched to motor inrush is required. The interrupting ratings are substantial: 187 kA at 240 V, 121 kA at 415 V and 440 V, 75.6 kA at 500 V, and 17 kA at 690 V — so it handles high-fault-current scenarios at distribution-level voltages without cascading upstream. Note the thermal derating: the breaker carries its full 500 A from 40 °C through 50 °C, then drops to 495 A at 55 °C, 490 A at 60 °C, and 485 A at 65 °C. At 70 °C ambient it still holds 480 A. That derating curve matters when the breaker is enclosed in a warm panel or mounted near other heat sources.
Auxiliary and trip configuration
The breaker ships with a shunt trip (STL) auxiliary release, a 2-auxiliary-switch plus 1-trip-alarm-switch HQ contact block, and a voltage-trip indicator. The basic switch supplied as the core is order code 3VA2450-5MN32-0AA0; the integrated auxiliary trip is 3VA9688-0BL32. No undervoltage release, no ground-fault monitoring, and no communication function are included on this variant. The maximum power loss is 99 W, which factors into thermal management inside the enclosure.
Physical footprint and environmental limits
Dimensions are 138 mm wide by 248 mm high by 110 mm deep. That 110 mm depth is the overall body depth — important for shallow enclosure fit. Operating temperature range is -25 °C to 70 °C; storage range extends from -40 °C to 80 °C. Rated insulation voltage Ui is 800 V. The latching endurance is rated at 15,000 operations, which is typical for an MCCB in motor-starting service where it cycles less frequently than a contactor.