The Siemens 4EU4321-4AA00-0A is a three-phase commutating choke (Kommut.-Drossel f. Stromrichter) designed for the DC link of line-commutated converters and drives. Its job is to limit the rate of rise of fault current and reduce harmonic distortion during commutation — critical for protecting thyristor stacks and smoothing the current waveform on high-power drives. Rated at 819 A continuous (LN) with a maximum of 910 A at 50 Hz, it handles the sustained current draw of a large converter feeding a motor load in a rolling mill, extruder, or pump drive. The 0.039 mH inductance is deliberately low — just enough to control di/dt without adding excessive voltage drop (4 % relative inductive drop at rated current). The 500 V AC operating voltage matches standard three-phase supply rails in European industrial plants. Thermal class H (180 °C winding hot-spot) per IEC 60085 means this choke takes the radiant heat near furnace zones without derating — a spec that matters when it's mounted inside a drive cubicle close to the line reactor.
The 910 A maximum rating is the thermal limit under worst-case converter commutation — not a continuous load figure. For continuous duty, size against the 819 A rated current (LN). The 4 % relative inductive drop at rated current tells you the voltage sag across the choke under full load; if your drive's DC-link voltage margin is tight, that drop must be factored into the bus voltage budget. Total power loss is 824 W (459 W coil + 365 W iron core) at rated conditions. That's heat that must be evacuated from the enclosure — plan forced ventilation or a larger cubicle if the choke is enclosed. Flat-type terminals for the main circuit accept busbar or large cable lugs — no screw-clamp or spring-cage connection. Verify your panel's busbar interface matches the flat terminal geometry before specifying.
Commutating chokes of this class are installed in the DC link between the converter bridge and the DC bus, typically in variable-speed drives for induction or synchronous motors. The 3-phase 50 Hz rating aligns with standard European industrial supply; the choke is sized for the converter's peak commutation current, not the motor's full-load amps. Mounting is open-frame inside a control cabinet or drive cubicle. The 0.265 m depth, 0.46 m width, and 0.435 m height require a panel cutout or mounting plate sized to those footprints. No DIN-rail clip — this is bolted down.
Lifecycle status is listed as mature — no active discontinuation notice, but not in the new-product-introduction phase either.