What this MCCB is and what the ratings mean for your panel
The Siemens SENTRON 3VA1050-4ED42-0KC0 is a 4-pole molded case circuit breaker (MCCB) rated for line protection, carrying 50 A continuously at 40 °C ambient and derating to 45 A at 70 °C — so in a warm enclosure you lose about 10 % of the headroom. The 121 kA breaking capacity at 240 V AC tells you it can safely interrupt a fault up to that level without upstream fuses or a larger breaker taking over; at 415 V the interrupting rating is still 75.6 kA, which covers most industrial distribution panels fed from a typical MV/LV transformer. The rated insulation voltage of 800 V means the internal clearances and creepage are designed for 690 V systems, so it fits European 400/690 V networks without derating the insulation.
Dimensions and panel fit
The breaker measures 70 mm deep, 101.6 mm wide, and 130 mm high. That 101.6 mm (4-inch) width is the standard footprint for a 4-pole SENTRON 3VA frame — it occupies four 25.4 mm module positions on a DIN rail or panel-mount backplate. Verify the gland-plate cutout and busbar spacing against your existing panel layout; the depth of 70 mm leaves room for rear-connected busbars or a shunt-trip accessory.
Built-in auxiliary and shunt trip
Factory-fitted with two auxiliary switches HQ and a shunt trip release (STL). The shunt trip allows remote tripping from a safety relay or emergency-stop circuit — useful for a tire-curing press where you want to drop power if the steam pressure exceeds the limit. The auxiliary switches report the breaker position back to a PLC or status lamp without adding a separate contact block.