The Siemens 4EU4351-0UB00-0A is a three-phase mains choke (line reactor) for variable-frequency drives, rated 1125 A continuous with a 1250 A maximum at 690 V AC, 50 Hz.
The 20 µH inductance (0.0203 mH) and 2% impedance are sized for a 1125 A drive input. That inductance value is what determines the harmonic attenuation and the peak current limiting — not the physical size. Total power loss is 940 W (690 W coil + 250 W iron core) at rated load and 40 °C ambient. That heat must be vented — IP00 means no enclosure, so it's intended for cabinet mounting with forced air or sufficient natural convection clearance. Class H insulation (180 °C thermal class per IEC 60085) gives margin for overloads and higher ambient conditions inside a panel. Flat-type terminals for the main circuit mean the connection uses busbar or compression lugs, not cable lugs. Factor that into your panel wiring plan — you'll need a transition to cable if the drive input uses ring terminals.