What it is — and what the ratings mean for your panel
The Siemens SENTRON 3VA1120-4ED16-0AA0 is a 1-pole molded case circuit breaker (MCCB) designed for line protection in distribution panels. Its 20 A rating holds flat from 40 °C through 55 °C, only stepping to 19 A at 60 °C and above — so in a typical 40 °C panel environment you get the full 20 A without derating. That 9 kA interrupting capacity at 415 V AC is the number that governs fault clearance on a 400 V three-phase line; the 75.6 kA at 240 V is what you'd see on a single-phase 240 V service, but the 415 V figure is the one that decides whether this breaker clears a bolted fault upstream of a motor branch. The TM210 overcurrent release combines a thermal bimetal for overload protection and a magnetic coil for short-circuit trips — standard thermal-magnetic action, no electronic adjustments. At 25.4 mm wide (1 inch), it occupies a single pole space on the DIN rail, matching the footprint of a standard miniature breaker but with the higher SCCR of a molded-case construction.
Integration — what fits where
The 70 mm depth (2.76 in) and 130 mm height (5.12 in) mean it clears most standard 200 mm deep enclosures with room for wiring gutters. IP40 on the front — protected against tools and wires >1 mm, but not sealed against moisture; keep it in a clean indoor panel or add a cover for washdown zones. The 4 W maximum power loss is negligible in a populated distribution board, but if you're packing 40 of these in a small cabinet, sum the losses against the enclosure's dissipation rating.
What the 415 V and 125 V ratings tell you
Rated operating voltage is 415 V AC and 125 V DC — the AC figure matches standard three-phase line-to-line voltages in 400 V grids; the DC figure covers control circuits or battery-backed loads at 125 V nominal. The 500 V rated insulation voltage means the internal clearances and creepage are designed for 500 V systems, so it can be used in 480 V panels (common in North America) as long as the operating voltage stays within the 415 V AC limit.