The Siemens 3VA2225-5KP42-0DK0 is a 4-pole IEC molded-case circuit breaker on the 250 A frame, built for line protection with an ETU850 electronic trip unit. The 55 kA interrupting rating at 415 V (class M) means it clears high-fault currents in a main distribution panel or large motor control center without needing an upstream current-limiting fuse — that's the kind of SCCR headroom a site electrical engineer wants for a 400 V bus with transformer-fed fault levels. The ETU850 provides LSI protection: long-time pickup adjustable 100 A to 250 A (Ir), short-time pickup 0.6 to 10× In, and instantaneous pickup 1.5 to 10× In. The neutral conductor protection is adjustable from OFF up to 100% of phase pickup, which matters for 4-wire systems where the neutral carries harmonic currents. An undervoltage release (UVR) rated 208–230 V AC 50/60 Hz is integrated — if the control voltage drops, the breaker trips, preventing automatic reclosure on a lost utility feed.
The UVR coil voltage (208–230 V AC) is common for North American 208Y/120 V or 240 V delta control circuits; verify compatibility with your panel's control transformer tap.
Mounts on a standard DIN rail or panel-mount baseplate — the 3VA2 frame is sized for 250 A continuous, so plan for M10 or similar bolted busbar connections on the line and load terminals. The UVR coil draws continuous power when the breaker is closed; if the control supply is switched separately, interlock it so the UVR cannot be energized with the breaker open and the trip mechanism unlatched.