The Siemens 4EU3921-0BS00-0A is a 3-phase commutating choke (line reactor) designed for converter front ends, rated 400 V AC with a maximum continuous current of 600 A and a nominal rated current of 540 A.
The 600 A maximum current (540 A rated) and 400 V AC three-phase rating place this choke squarely in heavy industrial converter duty — think large VFD input sections, DC bus supplies for multi-drive line-ups, or regenerative converter stages. The 0.1 mH inductance is low enough to keep voltage drop modest at line frequency (50/60 Hz) while still providing the commutation notch filtering a 6-pulse or 12-pulse rectifier needs. Thermal class H (180 °C) insulation means the winding can handle sustained overloads in a 55 °C ambient without accelerated aging — a real concern in enclosed converter cabinets with limited airflow. The flat-type terminals (bus-bar style) are designed for bolted connections with copper bars or heavy cable lugs — not screw-clamp or spring-cage terminations. Panel builders should plan for bus-bar routing and adequate clearance around the 0.41 m wide, 0.385 m tall, 0.229 m deep body.