What it is and what it does
The Siemens 3VA1050-4ED36-0KH0 is a SENTRON molded case circuit breaker (MCCB) for line protection — the main disconnect and fault interrupter in a distribution panel or motor control center. Three poles, rated continuous current Iu of 50 A, with a TM210 thermal-magnetic overcurrent release that handles both overload (thermal) and short-circuit (magnetic) trip curves. The 121 kA breaking capacity at 240 V AC is the headline number for fault clearing; at 415 V it still holds 75.6 kA, and at 690 V it drops to 11.9 kA — the voltage-dependent SCCR matters for the point of common coupling in your system.
Current derating and thermal reality
Rated 50 A continuous, but only up to 50 °C ambient — above that the TM210 release starts to thermally limit. At 55 °C it carries 48 A, at 60 °C it's 47 A, at 65 °C it's 46 A, and at 70 °C it's 45 A. If your panel internal ambient runs hot (enclosed, sun-loaded, next to drives), size the load side for the derated figure, not the nameplate 50 A. The storage range is -40 to 80 °C; operating ambient is -25 to 70 °C.
Integrated auxiliary and shunt trip
This variant ships with 2 auxiliary switches plus 1 trip alarm switch (HQ configuration), and a shunt trip release (STL) for remote tripping — no undervoltage release, no communication module, no ground-fault monitoring. The shunt trip is the integrated auxiliary release design; its order code is 3VA9688-0BL33. If you need remote undervoltage protection or Modbus communication, this is not the variant — look at the 3VA1 family with electronic releases.
Panel fit and mounting
Front IP40 protection class — suitable for enclosure mounting behind a door or cover, not for washdown. Dimensions: 130 mm height, 76.2 mm width (3-pole standard), 70 mm depth. The width is the critical dimension for multi-pole grouping in a panel; depth of 70 mm means it clears most 200 mm deep enclosures with room for wiring gutters. Latching endurance is 15,000 operations — not a high-cycle switching device, but fine for infrequent disconnect duty.