Line protection MCCB with integrated undervoltage release
The Siemens SENTRON 3VA1120-3EF32-0CC0 is a 3-pole molded case circuit breaker (MCCB) rated for line protection, carrying a continuous current Iu of 20 A at 40 °C through 50 °C, with a TM240 thermal-magnetic overcurrent release. Its interrupting capacity reaches 75.6 kA at 240 V AC, 52.5 kA at 415 V AC, 32 kA at 440 V AC, and 10.5 kA at 690 V AC — figures that govern fault-clearing capability in distribution panels where the available fault current is known. The breaker includes an integrated undervoltage release (UVR) and two HQ auxiliary switches, but no communication function, phase failure detection, or ground fault monitoring — a straightforward protection device for standard feeder circuits.
Thermal derating and panel integration
Rated continuous current holds at 20 A from 40 °C to 50 °C ambient, then derates to 19.2 A at 55 °C, 18.8 A at 60 °C, 18.4 A at 65 °C, and 18 A at 70 °C — a linear drop of roughly 0.4 A per 5 °C step above 50 °C that must be factored into panel thermal calculations. Dimensions are 130 mm height, 76.2 mm width, 70 mm depth, with IP40 protection on the front — fits standard SENTRON mounting footprints and panel cutouts for 3VA frame sizes. Operating temperature range -25 °C to 70 °C; storage range -40 °C to 80 °C. Mechanical endurance 15,000 cycles.
What the interrupting ratings mean for coordination
The 75.6 kA at 240 V and 52.5 kA at 415 V are the maximum fault currents this MCCB can safely interrupt at those voltages — critical for selectivity studies where the upstream breaker must have a higher or equal interrupting rating to avoid cascading failure. Rated insulation voltage Ui is 800 V, so the breaker is suitable for 690 V AC systems despite the lower interrupting capacity at that voltage (10.5 kA). The TM240 release is a fixed thermal-magnetic type, not electronic — no adjustable long-time or short-time pickup curves.