Line protection MCCB with UVR — 50 A, 121 kA at 240 V
The Siemens SENTRON 3VA1050-4ED36-0CH0 is a 3-pole molded case circuit breaker (MCCB) rated for line protection, carrying a continuous current Iu of 50 A up to 40 °C and derating to 45 A at 70 °C. Its TM210 thermal-magnetic overcurrent release handles overload and short-circuit protection in one package. The 121 kA breaking capacity at 240 V is the headline figure for high-fault panels; at 415 V it still holds 75.6 kA, and at 690 V it drops to 11.9 kA — so the SCCR you need for your transformer secondary or bus tie determines the voltage you spec against.
What the ratings mean for fit
The 50 A frame is thermally rated — it holds 50 A continuously at 40, 45, and 50 °C ambient, then steps down to 48 A at 55 °C, 47 A at 60 °C, 46 A at 65 °C, and 45 A at 70 °C. If your panel ambient runs above 50 °C, you need to account for that 5 A drop. The 800 V rated insulation voltage (Ui) means it's suitable for 480 V and 600 V class systems with margin. The IP40 front protection keeps dust out of the panel face — fine for a clean indoor enclosure, not for washdown zones.
Integrated undervoltage release and auxiliary contacts
This MCCB ships with an undervoltage release (UVR) built in — part of the order code's 4ED36 suffix. That UVR trips the breaker when control voltage drops below a threshold, which is standard for safety circuits that need a drop-out on power loss. The auxiliary contact block provides 2 auxiliary switches plus 1 trip alarm switch (HQ type), giving you status feedback for PLC or panel indication without a separate add-on module. The latching endurance is rated at 15 000 operations — mechanical life for the mechanism, not the electrical breaking count.