Commutating Choke for Converter Duty
The Siemens 4EU4321-0DC00 is a three-phase commutating choke designed for converter applications, rated at 650 A continuous and 400 V AC. With an inductance of 97 µH and a relative inductive voltage drop of 0%, it limits current rise during commutation events in the converter's DC link or AC input, protecting the semiconductor switches from di/dt stress. The choke is wound for thermal class H (180 °C) per IEC 60085, with a combined power loss of 670 W in the coil and 365 W in the iron core at rated conditions.
Sizing and Thermal Considerations
The DC equivalent rating is 796.5 A, which matters when the choke is used in a six-pulse converter where the DC link current is roughly 1.225 times the AC line current. The 670 W coil loss plus 365 W iron loss means the choke dissipates over 1 kW at full load — plan for forced ventilation or generous cabinet volume to keep the ambient below 40 °C. The flat-type terminals accept busbar or cable lugs for the main current circuit. Panel builders should verify the terminal dimensions against their lug width — the 0.46 m width and 0.435 m height give enough clearance for 650 A cable routing, but the 0.265 m depth is shallow enough for most 800 mm deep enclosures.