What it is and what it does
The Siemens 3VA1120-5EE32-0AA0-ZD00 is a 3-pole IEC frame 160 molded-case circuit breaker with class M breaking capacity — 55 kA at 415 V. That rating means it can safely interrupt fault currents up to 55,000 A at 415 V without welding contacts or rupturing the case, which is what you need for high-fault panelboards or distribution downstream of a large transformer. The thermal-magnetic trip unit (TM220, ATFM) gives you adjustable overload protection from 14 A to 20 A and a fixed short-circuit pickup at 16 times the rated current (In=20 A).
What the ratings mean for panel fit
The 55 kA interrupting rating at 415 V is the headline number for this breaker — it tells you the maximum fault current the device can clear without failing. In a real panel, that governs whether the breaker coordinates with upstream gear (transformer secondary, main breaker) and whether it meets the available fault current at its mounting point. The adjustable overload Ir (14–20 A) lets you dial in the exact motor or feeder load without swapping trip units, which saves a panel rewire if the load changes slightly.