The Siemens 4EP3900-3DS00 is a three-phase commutating choke (line reactor) designed for converter front-ends. Rated inductance is 0.57 mH at 50 Hz, with a relative inductive voltage drop of 4% at rated current — that 4% figure is the impedance the choke presents to the line, which governs how much it smooths the DC link and limits harmonic distortion. Operating voltage is 500 V AC. Power loss splits into 65 W in the coil and 16.5 W in the iron core at rated conditions and 40 °C ambient. Thermal class B per IEC 60085 means the insulation system is rated for a 130 °C hot-spot temperature — adequate for continuous duty in a ventilated cabinet, but derate if the enclosure runs hot.
Enclosure is IP00 — open frame, no finger protection. Mount it inside a locked cabinet or behind a panel door. Dimensions are 0.219 m wide by 0.179 m tall by 0.123 m deep, so it fits a standard 220 mm DIN-rail backplate with room for a contactor and fuse holder alongside. Connections are screw-type terminals sized for the main circuit current.