The Siemens 4EU3021-0AQ00-0A is a commutating choke (line reactor) designed for converter applications in three-phase AC systems. It sits between the supply and the converter input, limiting current rise rates and reducing harmonic distortion on the line side.
That 4% drop is typical for a line reactor — enough to smooth commutation notches and limit fault current, but low enough to keep voltage sag on the DC bus within a few percent. The 283 W copper loss plus 209 W iron core loss (492 W total at full load) means this choke dissipates heat; it's not a sealed unit. IP00 protection confirms it's for cabinet mounting only — no washdown, no dust ingress protection. The thermal class H insulation (180 °C rated) gives headroom for the heat generated in a crowded panel.
Dimensions are 0.3 m wide, 0.269 m tall, 0.221 m deep — a substantial block that needs a solid mounting plate and clearance for airflow. The 55 °C ambient temperature rating means it's rated for a warm enclosure; derate above that. Mount it close to the converter line input to keep the inductive loop tight.