Commutating Choke for High-Current Converter Lines
The Siemens 4EU3921-3BA00-0A is a three-phase commutating choke built for converter duty — it sits on the AC side of a drive or rectifier to limit di/dt and smooth the current waveform during commutation. Rated at 900 A continuous (1000 A maximum) with a peak surge capacity of 1250 A, it handles the kind of sustained load you'd see on a large pump, conveyor, or compressor drive running off 400 V AC, 50 Hz mains. That low impedance is intentional: it provides just enough reactance to protect the converter's thyristors or IGBTs from excessive current rise rates without dropping significant voltage under load. The flat-type terminals (bus-bar style) suit bolted connections to the main power circuit, common in high-current industrial panels.
Ratings That Matter for the Buyer's Decision
The 900 A rated current (1000 A max) and 1250 A peak define the choke's thermal and magnetic headroom. For a 400 V, 50 Hz converter line pulling 900 A continuous, this choke stays within its thermal class H insulation (200 °C rated, per IEC 60085) — meaning it can run hot without cooking the winding. The combined copper and iron losses total 596 W (380 W coil + 216 W iron core), so factor that heat into your cabinet ventilation. The DC rated current of 1225.4 A confirms the choke can also handle DC-side ripple currents in six-pulse rectifier configurations, though the primary rating is AC at 50 Hz. The 4% voltage drop at rated current is typical for commutating chokes in this class — it's enough to limit fault current rise without causing noticeable voltage sag in normal operation.