The Siemens 4EU3052-2UA00-0AA0 is a three-phase mains choke (line reactor) designed for the input of a frequency converter (Netzdrossel f. FU). It sits between the supply and the drive to limit harmonic distortion, reduce reflected-wave stress on the motor, and provide a measure of short-circuit current limitation. Rated at 405 A continuous with a maximum of 450 A, it handles the full-load current of a large drive — think 200+ kW motor loads on 500 V AC three-phase mains.
The 405 A rated current (I LN) is the continuous current the choke can carry at its rated 500 V AC, 50 Hz without exceeding a 40 °C ambient. The 450 A maximum (Ithmax) is the thermal limit under overload — useful for short-duration peaks, but the continuous duty is the 405 A figure. The 2 % relative inductive voltage drop (UK) means the choke's impedance is sized to drop 2 % of rated voltage at rated current; this is a standard value for drive input reactors, balancing harmonic attenuation against voltage sag. The 0.04 mH inductance (0.00004 H) is the per-phase value that, combined with the 2 % drop, tells you this is a relatively low-impedance reactor — it's meant for the line side, not the motor side.
Thermal and mechanical design
Total power loss is 322 W — 220 W in the coil and 102 W in the iron core — all dissipated as heat inside the panel. Thermal class H (IEC 60085) means the insulation system is rated for 180 °C hot-spot temperature, giving headroom above the 40 °C ambient. Connections are flat-type terminals (bus-bar style), so you'll need lugs or flat copper bars, not ring terminals on stranded wire.