The Siemens 4EU4321-5CA00-0A is a 3-phase commutating choke for converter applications, rated 900 A continuous with a peak current capability of 1 250 A. It operates at 500 V AC, 50 Hz, and provides 29 µH inductance with a 4% relative inductive voltage drop at rated current. The choke is designed for use in power conversion circuits where it limits di/dt and reduces harmonic stress on semiconductors.
Key Ratings and What They Mean
The 900 A rated current is the continuous thermal current at 40 °C ambient — this is the line current the choke can carry without exceeding its thermal class H insulation. The 1 250 A peak rating covers transient overloads typical during converter startup or fault clearing. Inductance of 29 µH with a 4% voltage drop at rated current means the choke introduces a predictable impedance into the converter commutation path, limiting current rise rates and protecting the switching devices. The 480 W coil loss plus 274 W iron core loss total 754 W — factor this heat into your enclosure ventilation. IP00 protection class means the choke is open-frame — no ingress protection. It must be mounted inside a cabinet with adequate clearance and cooling. Flat-type terminals accept busbar or cable lugs; plan for bolted connections, not spring clamps.
Where It Is Used
This choke sits between the converter (VFD or DC drive) and the supply line, or in the DC link, to suppress commutation notches and limit fault current. Common in industrial drive systems for pumps, conveyors, and compressors where a 3-phase 500 V AC supply feeds a converter rated near 900 A.