The Siemens 4EU4321-8AA00-0A is a three-phase commutating choke designed for converter applications. It carries a maximum current of 630 A at 50 Hz and a rated continuous current of 567 A, with an operating voltage of 690 V AC. The rated inductance is 0.076 mH, and the relative inductive voltage drop is 4% at rated current and frequency. These ratings define the choke's ability to limit di/dt and smooth commutation notches in the DC link of a line-commutated converter — a critical role in protecting the thyristors or IGBTs from excessive turn-on stress and reducing harmonic injection back onto the supply.
That means the choke can carry 567 A indefinitely without exceeding its insulation temperature limit — a key number for sizing the DC-link bus. The 630 A maximum (I thmax) is a short-time thermal limit at 50 Hz, not a continuous rating. The 772 A DC rated value tells you the choke can handle a DC bias current of 772 A when used in a DC-link application, which is higher than the AC rating because the RMS current in the DC link is lower for the same copper loss. The 4% voltage drop is the impedance at rated current — it sets the commutation notch attenuation and determines whether the converter's control loop sees enough voltage margin. The 480 W coil loss plus 325 W iron core loss (805 W total at rated conditions) must be dissipated in the enclosure; IP00 means the choke is open-frame and relies on the cabinet's forced-air or natural convection — no integral fan.
Integration and physical fit
The choke measures 0.46 m wide by 0.435 m high by 0.265 m deep — a substantial footprint that needs to be accounted for in the cabinet layout. The main current circuit connects via flat-type terminals (busbar or flat-cable lugs), not screw clamps or spring cages. No DIN-rail mounting; this is a bolt-down component. The open-frame IP00 construction means it must be installed inside a suitable enclosure with proper clearance to grounded metalwork and adequate ventilation for the 805 W total loss.