The Siemens 4EU2522-1AA08-0AA3 is a 3-phase commutating choke for converter applications — what you'd call a line reactor in plain English. It's rated for 400V AC at 50Hz, with a maximum continuous current of 125A and a rated value of 112.5A. That 4% drop figure is the key number for sizing: it tells you how much voltage the choke eats at full load. Out here in the grease, a choke like this sits between the line and a variable-frequency drive or DC drive, smoothing out the harmonics and protecting the rectifier from nasty current spikes. If you've ever buried a drive because the line was too dirty, you know the value of a properly sized reactor. The winding is Class H insulation per IEC 60085, good for a 40°C ambient. That's the thermal class for high-temperature spots — motor control centers near ovens or in hot machine rooms. The IP20 housing means it's for indoor panel use only, not washdown areas.
Physical footprint: 0.225m wide, 0.21m tall, 0.16m deep. That's a panel-mount part, not DIN-rail. The flat-type terminals on the main circuit take a busbar or a heavy lug — no spring-cage here. Plan for bolted connections and enough clearance around the terminals for a wrench. The 112.5A rated current is the continuous figure for a 40°C ambient. If your panel runs hotter, derate accordingly. The 125A maximum is the thermal limit under the same conditions — don't plan to run at 125A continuously unless you've got airflow or a lower ambient.