What it is and what it does
The Siemens 4EU3952-0AD00-0A is a three-phase mains choke (Netzdrossel) rated for 600 V AC and 100 A maximum current, with a 1 mH inductance. It's designed to sit between the supply and a drive or converter, smoothing current ripple and limiting harmonic distortion on the line side. The 4% relative inductive voltage drop at rated current tells you the choke is sized for typical drive input filtering — not a heavy-duty harmonic trap, but enough to keep a VFD from hammering the upstream transformer.
Key ratings and what they mean for fit
Rated operational current is 90 A, with a 100 A AC maximum — the extra headroom covers short-term overloads during motor acceleration. The 20 Hz operating frequency is the fundamental line frequency this choke is tuned for; don't expect it to perform the same at 50/60 Hz without checking the saturation curve. Thermal class H (180 °C insulation system) means it can live in a hot cabinet or near a drive heatsink without cooking the windings. IP00 means no enclosure — mount it inside a panel with proper clearance, and keep fingers and tools away from the flat copper connectors.
Where it goes in the panel
At 0.41 m wide, 0.385 m tall, and 0.229 m deep, this is a substantial iron-core choke — plan for a dedicated mounting plate or heavy DIN-rail bracket. The flat connector main circuit terminals accept busbar or cable lugs; torque them per the manufacturer's spec (not listed here, but standard for the class). Power loss totals 794 W (517 W coil + 277 W iron core) at full load — that's real heat that needs ventilation or forced air in the enclosure. Ambient rated at 55 °C; derate if your panel ambient runs higher.