The Siemens 3VA1120-5GE42-0AA0-ZD00 is a 4-pole IEC frame 160 molded case circuit breaker (MCCB) with a 55 kA breaking capacity at 415 V — that's breaking capacity class M, meaning it clears high-fault currents on industrial distribution without cascading upstream. Rated In=20 A with TM220 thermal-magnetic trip, overload adjustable Ir=14 A…20 A, and fixed short-circuit pickup Ii=16 x In (320 A). The N conductor is protected at 100%.
The TM220 thermal-magnetic unit gives you adjustable overload (Ir) via a dial on the front, so you can set it to match the cable or load without swapping the breaker body. Fixed magnetic pickup at 16 x In means it's a standard motor-starting curve, not a selective or electronic trip — fine for general distribution or feeder protection where you don't need zone selectivity. The 100% N conductor protection means the neutral pole trips at the same rating as the phases — required for some configurations with harmonic loads or where neutral current can approach phase current. The nut keeper kit is a small detail but saves time on the panel build: no loose hardware to drop into the enclosure.
Deployment context
The DC Power OEM designation means it's built into a DC power supply or UPS system manufactured in China, so the breaker is the line-side protection for the rectifier input.