The Siemens SIDAC 4EM5207-2CB00 is a single-phase smoothing choke — a DC link reactor — designed to reduce ripple current and harmonic content on DC bus lines in drives, converters, and power supplies. It carries a maximum DC current of 21A, with a rated continuous current of 18.9A, at an operating voltage of 690V. The 7mH inductance smooths the current waveform, protecting downstream capacitors and extending their service life. Rated for 300 Hz switching frequency, it matches the typical PWM carrier frequencies found in modern variable-frequency drives and DC-DC converters. The 28.4W coil loss and 0.6W iron core loss give a total power loss of 29W at rated load — figure that into your enclosure thermal budget.
IP00 means it's an open-frame component — mount it inside a panel or cabinet with proper clearance to live parts and airflow. Dimensions are 0.121m wide by 0.131m high by 0.128m deep, so it occupies about a 5-inch cube. The screw-type main circuit terminals accept standard ring or fork lugs; plan for 0.2–2.5 mm² conductors per typical choke wiring practice. Thermal class B per IEC 60085 means the insulation system is rated for 130°C hot-spot temperature. With a 40°C ambient rating, you've got a 90°C rise budget — adequate for most industrial panel environments, but derate if your enclosure runs hot.