It sits between the supply and the converter's input, smoothing current ripple and limiting fault-current rise rates. Rated for continuous 800 A at 750 V AC, it's built for heavy industrial drives and power conversion stages where the line-side harmonics or commutation notches need iron-core damping. The core inductance is 68 µH (0.000068 H) with a relative inductive voltage drop of 4% at rated current and frequency — that's the design spec that governs how much line-side voltage sag the choke introduces. At 800 A and 50/60 Hz, that 4% drop is the trade-off for the current-limiting and harmonic attenuation you get. Total power loss comes to about 904 W — 500 W in the coil and 404 W in the iron core — all dissipated as heat at 40 °C ambient. That's not a small number; the panel builder needs to account for that thermal load in the enclosure's ventilation or forced-air cooling.
The 4EU4521-2AA00 measures 0.460 m wide by 0.435 m tall by 0.293 m deep — roughly 18 by 17 by 11.5 inches. It's an open-frame (IP00) assembly, so it's meant for installation inside a ventilated cabinet, not out on the plant floor where dust or washdown would get to it. The main current circuit connects via flat-type terminals, which means bus-bar or heavy cable lugs, not screw-clamp blocks. Thermal class H per IEC 60085 means the insulation system can handle 180 °C hot-spot temperature — that's the margin that lets this choke run hard in a 40 °C ambient without cooking the windings. It's a standard spec for industrial converter-duty reactors.