50 A MCCB with 121 kA SCCR — fit and thermal reality
The Siemens SENTRON 3VA1150-4EF36-0BC0 is a 3-pole molded case circuit breaker (MCCB) rated for line protection, carrying 50 A continuously at 40 °C and derating to 45 A at 70 °C. The interrupting capacity hits 121 kA at 240 V, 75.6 kA at 415 V, and holds 11.9 kA all the way to 690 V — so it handles high-fault panels without cascading upstream. Rated insulation voltage is 800 V, giving headroom on 480 V or 600 V systems.
Built-in undervoltage release and auxiliary switching
Factory-fitted with an undervoltage release (UVR) and two HQ auxiliary switches, this breaker drops the load on loss of control voltage — useful for motor feeder protection where a sag or dropout must trip the MCCB rather than let the contactor hold in. The auxiliary switches report position back to the PLC or status lamp without a separate limit switch.
Panel fit — dimensions and thermal budget
Measures 130 mm tall, 76.2 mm wide, 70 mm deep — a standard MCCB footprint for 3-pole frames up to 50 A. Maximum power loss is 17.1 W at rated load, so the enclosure must dissipate that heat; derating above 55 °C is gradual (49 A at 55 °C, 45 A at 70 °C), which matters in a sealed or high-ambient panel.