The Siemens 4EP3801-0US00 is a three-phase mains choke — what most of us call a line reactor — designed for the input of a variable-frequency drive. It's rated for 480 V AC, 50/60 Hz, with a maximum continuous current of 22.4 A and a rated current of 20.16 A at 40 °C ambient. The 1.3 mH inductance and 4 % relative voltage drop at rated current are what you'd expect for a drive input reactor sized to limit harmonics and smooth the line-side waveform. Total power loss splits into 73 W in the coil and 23 W in the iron core, for 96 W total at full load. That's heat that stays in the panel — the IP00 enclosure means no fan or ducting, so make sure the cabinet has enough free-air volume or forced ventilation to keep the ambient below 40 °C. Thermal class B (130 °C) insulation gives a reasonable safety margin above the 40 °C ambient.
Sizing and fit
Footprint is 0.178 m wide by 0.153 m tall by 0.12 m deep — about 7 by 6 by 4.7 inches. That's a compact package for a 20 A three-phase reactor. Screw terminals for the main circuit; no DIN-rail clip, so it bolts to a backplate or chassis. IP00 means no touch protection — mount it behind a locked door or inside a grounded enclosure.