MCCB for line protection with shunt trip
The Siemens 3VA1050-4ED32-0JA0 is a 3-pole SENTRON molded case circuit breaker (MCCB) designed for line protection, fitted with a TM210 thermal-magnetic overcurrent release and a factory-installed shunt trip (STL) auxiliary release. Rated 50 A continuously at 40 °C, it delivers a 121 kA interrupting capacity at 240 V — the figure that governs fault clearance on a 240 V line side. The 800 V rated insulation voltage supports use in 400/480 V distribution panels where the breaker sits downstream of a transformer.
Interrupting capacity across voltages
At 415 V the interrupting rating is 75.6 kA; at 440 V it drops to 52.5 kA, and at 500 V and 690 V it holds at 11.9 kA. For a 400 V three-phase panel, the 75.6 kA figure gives headroom above typical 25–50 kA available fault currents, so selectivity coordination with an upstream feeder breaker is straightforward. The TM210 release is a fixed thermal-magnetic type — no electronic adjustment, which simplifies spare-stocking but locks the trip curve to the factory setting.
Current derating and thermal limits
The breaker holds 50 A from 40 °C through 50 °C ambient. At 55 °C it derates to 49 A, at 60 °C to 48 A, at 65 °C to 46 A, and at 70 °C to 45 A. If the panel internal ambient runs above 50 °C — common in a sealed enclosure with other heat sources — the continuous load must be trimmed per the derating curve. Maximum power loss is 14.6 W, which matters for enclosure thermal rise calculations.
Physical fit and mounting
Dimensions are 130 mm height, 76.2 mm width, 70 mm depth. The 76.2 mm width (3 inches) is the standard 3-pole MCCB footprint for a 200 A frame — it occupies three 25 mm DIN positions if base-mounted, or bolts directly to a mounting plate. Depth of 70 mm leaves clearance behind a 120 mm deep enclosure door. No undervoltage release or communication module is fitted on this variant.