What this mains choke does for a drive line
The Siemens 4EU2551-3UB00-0A is a three-phase mains choke (line reactor) designed for the input side of a variable frequency drive. Its job is to smooth current harmonics, limit inrush current, and protect the drive's DC bus from line-side transients. Rated 90 A continuous with a 100 A maximum, it handles the full-load current of a substantial motor — think a 45–55 kW induction motor on a 400 V line — without saturating. The 0.37 mH inductance at 4 % voltage drop (relative inductive drop at rated current and frequency) is the key sizing parameter. That 4 % figure means the choke drops about 4 % of line voltage at full load, which is the standard sweet spot for drive input reactors: enough to reduce harmonic distortion to acceptable levels without robbing the drive of too much voltage headroom. It operates on 50 or 60 Hz lines, so it suits both European and North American mains. This is an open-frame (IP00) component — no enclosure, no finger-safe shrouds. It mounts inside a panel or drive cabinet where the surrounding equipment provides the physical protection. The flat-type terminals accept busbar or large-gauge cable lugs, typical for the power circuit of a drive input section.
Thermal class and ambient limits
The choke is built to thermal class H per IEC 60085, meaning its insulation system can withstand a continuous hot-spot temperature of 180 °C. That is the highest standard class for dry-type reactors and transformers — it gives headroom if the choke sits near a hot drive or in a poorly ventilated cabinet. The rated ambient temperature is 40 °C; above that, derate the continuous current per the manufacturer's thermal curve (not provided here, but standard practice for class H designs).
Panel integration notes
This is not a DIN-rail component. It is a bolted-frame reactor with flat-type terminals, sized for panel-mount installation. The footprint is 0.225 m wide by 0.21 m tall, with a depth of 0.176 m — allow clearance around it for airflow and for the busbar or cable bends to the flat terminals. IP00 means no touch protection; locate it behind a panel door or inside a locked cabinet.