The Siemens SENTRON 3VA1120-4EF32-0CH0 is a 3-pole molded case circuit breaker (MCCB) rated for 20 A continuous at 40 °C, with a breaking capacity of 121 kA at 240 V AC. That interrupting rating means it can safely clear a fault up to 121 kA without the arc flashing over to adjacent gear — critical for high-fault utility feeds or transformer secondaries where available fault current is high. The part carries an undervoltage release (UVR) and comes factory-fitted with two auxiliary switches plus one trip alarm switch (HQ). The UVR trips the breaker when supply voltage drops below a set threshold — useful for motor protection or sequence interlocking where a voltage sag should drop the load. The auxiliary contacts give the PLC a dry-contact status of the breaker position; the trip alarm signals a fault event separately. Sized for DIN-rail or panel-mount enclosures: 70 mm deep, 76.2 mm wide, 130 mm tall. The 3-pole footprint matches standard Siemens SENTRON 3VA panel cutouts, so a swap-in for a failed 3VA unit requires no re-drilling.
Breaking capacity and thermal derating
Breaking capacity drops with voltage: 121 kA at 240 V, 75.6 kA at 415 V, 52.5 kA at 440 V, and 11.9 kA at 500 V and 690 V. The 240 V figure is the highest — this breaker is at home in North American 240/120 V split-phase or 208Y/120 V wye panels where fault current can exceed 100 kA. At 415 V it still handles 75.6 kA, covering most European 400 V industrial feeds. Thermal rating holds 20 A from 40 °C through 55 °C. At 60 °C it derates to 19 A, and stays at 19 A through 70 °C. That flat derating curve means the breaker does not lose headroom quickly as ambient climbs — useful in a crowded panel where internal temperature can hit 55 °C without forcing a larger frame.