I believe you are talking about the filters to optimise to the load power factor. The VFDs have different features. It is essential to govern to gain the required output. Your output might be customising the speed, the frequency or even the voltage; when you do so the output will come out distorted, in order to tune the output you will need the reactors>Quality VFD's incorporate either an AC Reactor or DC Reactor (choke). Their inclusion in the basic design of the VFD allows the design engineer to maximize the advantages of the choke. Their function is to reduce the current distortion caused by the input stage rectifiers by slowing the rate of change of current, and thus charging the internal capacitor at a slower rate over a longer time.
