What it is and what it does
The Siemens SIDAC 4EU9951-0UA00 is a single-phase output reactor rated for 1080 A AC continuous current, designed to sit between a variable-frequency drive and the motor cable. It limits the rate of rise of voltage (dV/dt) and reduces capacitive charging currents in long motor leads, which protects the motor winding insulation and extends bearing life. The reactor is rated for a fundamental frequency range of 0 to 300 Hz and a switching frequency of 6 kHz, covering most PWM drive topologies in industrial use.
Key ratings and what they mean for fit
The 1080 A AC rating is the continuous current the reactor can carry without exceeding a 40 °C ambient temperature rise — sized for large drives in the 500–800 kW range depending on load duty. The 0.23 mH inductance value (with a 6.8 % voltage drop at rated current) determines the dV/dt suppression: higher inductance gives more filtering but also more voltage drop, so the 6.8 % figure is a standard trade-off for motor cable lengths up to about 300 m. Class H insulation (180 °C thermal class per IEC 60085) means the reactor can handle sustained overloads and high ambient temperatures without derating prematurely.
Where it goes and how it connects
This is an open-frame (IP00) component — no enclosure, so it mounts inside a panel or cabinet where the environment is clean and dry. The flat-type terminals accept busbar or large cable lugs; plan for a bolted connection rather than a spring clamp. Physical footprint is 0.37 m wide × 0.32 m deep × 0.24 m high, which fits a standard 800 mm wide cabinet with room for side cable ducts. Single-phase design means one reactor per motor phase; for a three-phase motor you need three units.