What it is and what it does
The Siemens 4EP3801-2DS00 is a commutating choke (line reactor) for converter applications — three-phase, 400 V AC, 50 Hz. It limits current rise and harmonics on the input side of a variable-frequency drive or DC drive, protecting the rectifier and smoothing the DC bus. Rated 31.95 A continuous with a 35.5 A maximum, it's sized for a 30–40 A drive input on a 400 V three-phase supply. Inductance is 0.79 mH with a 4% relative inductive voltage drop at rated current and frequency — a standard impedance for line reactors in this class. The choke is self-cooled (IP00, no enclosure), so it needs to be mounted inside a cabinet with adequate ventilation. Screw-type terminals for the main circuit make field wiring straightforward.
Ratings and what they mean for fit
The 35.5 A maximum (Ithmax) is the thermal continuous current the choke can carry without exceeding a 40 °C ambient. The 31.95 A rated current (ILN) is the nominal operating point for the 4% voltage drop — if your drive draws 32 A continuously, this choke matches. At DC, the rated value is 43.5 A, so it also works on the DC bus of a converter if needed. Power loss splits into 53 W in the coil and 18 W in the iron core at rated conditions — total 71 W. That's heat that stays in the cabinet; factor it into your enclosure cooling calculation. Thermal class B (130 °C) insulation gives a reasonable safety margin for continuous duty.