The Siemens 4EU4521-0AL00 is a 3-phase commutating choke (Kommut.-Drossel f. Stromrichter) sized for converter output circuits. It carries a rated continuous current of 1640 A at 400 V AC, with an inductance of 0.017 mH (17 µH). That inductance value is deliberately low — it's not a line-reactor for harmonic filtering; it's a fast-saturating choke that limits the di/dt during thyristor or IGBT commutation events in the converter bridge. The IP00 rating means it's an open-frame component — no enclosure, no finger-safe guarding. It goes inside a converter cabinet or a dedicated panel section where the upstream IP rating handles the environment.
That's the current the choke can carry without exceeding its Class H insulation temperature rise (180 °C hot-spot per IEC 60085). In practice, if your converter's output RMS current hits 1640 A at 40 °C ambient, this choke is thermally matched. Above that ambient, derate per the winding thermal curve — Class H gives headroom, but the iron-core losses (435 W) are fixed with voltage and frequency, so the total loss doesn't scale linearly with load. The DC rated value of 2009.8 A is a separate figure: it tells you the choke can handle a DC current component that high, which matters for six-pulse or twelve-pulse rectifier circuits where the DC link ripple current flows through the commutation path.