What this output reactor does
The Siemens SIDAC 4EU4521-0CD00-0B is a 3-phase output reactor (output choke) for variable-frequency drive installations. It sits between the drive output and the motor, filtering the PWM carrier to reduce voltage spikes, limit motor bearing currents, and extend cable runs. Rated for a 6.4 kHz switching frequency and a maximum continuous current of 111 A, it handles the output of a 400 V-class drive in the 75–100 kW range depending on duty cycle.
The 111 A maximum rating is the thermal limit at 40 °C ambient — derate above that. The 0.4 mH inductance is a common value for motor cable lengths up to about 150 m on a 400 V drive; longer runs typically need a higher inductance reactor. The 6.4 kHz switching frequency matches most modern IGBT drives; if your drive runs a higher carrier frequency, the core losses increase and you may need to derate current or step up to a reactor rated for that frequency. Thermal class H insulation means the winding can handle 180 °C hot-spot temperature — adequate for the reactor's own losses plus heat soak from the drive cabinet.
Physical integration and termination
The reactor measures 0.46 m wide by 0.43 m tall by 0.29 m deep — a substantial block that needs floor or back-panel mounting, not a DIN rail. IP00 means no enclosure; it must live inside a cabinet with at least IP2X protection. Main circuit connections are flat-type terminals, designed for busbar or cable lug termination — not spring-cage or screw-clamp. Plan for M8 or M10 ring lugs and adequate bending radius for the incoming motor cables.