What it is and what it does
The Siemens SENTRON 3VA1050-4ED42-0BH0 is a 4-pole molded case circuit breaker (MCCB) rated for line protection, with a continuous current Iu of 50 A and a TM210 thermal-magnetic overcurrent release. Its interrupting capacity reaches 121 kA at 240 V, 75.6 kA at 415 V, 52.5 kA at 440 V, and 11.9 kA at 690 V — so it clears high-fault currents on the secondary side of a distribution transformer or at a main feeder without upstream coordination issues.
Rating so-what and thermal derating
The 50 A rating holds flat from 40 °C through 50 °C ambient; above that it derates to 48 A at 55 °C, 47 A at 60 °C, 46 A at 65 °C, and 45 A at 70 °C. If the panel ambient runs above 50 °C, size the load at the derated value — the TM210 release does not compensate for enclosure heat rise. Rated insulation voltage Ui is 800 V, and the front face carries IP40 protection — fine for a clean indoor panel but not for washdown zones.
Auxiliary and undervoltage release
This MCCB includes an integrated undervoltage release (UVR) plus 2 auxiliary switches and 1 trip alarm switch (HQ configuration). The UVR drops the breaker when control voltage falls below the dropout threshold — standard for emergency-stop chains or undervoltage protection on motor feeders. The auxiliary and alarm contacts let a PLC or SCADA system confirm the breaker state without a separate status relay.
Panel fit and integration
Dimensions are 70 mm deep, 101.6 mm wide, and 130 mm high — a standard MCCB footprint for a 4-pole 50 A frame. It mounts on a DIN rail or directly to a backplate; the 70 mm depth leaves clearance for a standard 200 mm deep enclosure with wiring gutters. The TM210 release is fixed-trip, not adjustable, so set the load-side protection at the downstream breakers.