AC Drive Manufacturers

On the line side of an AC drive, the problem is generally distortion power factor rather than displacement and passive harmonic filters for 5th, 7th etc. are sometimes used to mitigate the effects of the harmonics. And to comply with agreed contract limits on voltage distortion. One of the constraints is that the filters are capacitive at the fundamental and, with no lagging displacement power factor to correct, there is the risk of leading power factor. Active harmonic correction that uses both capacitos and inductors that are switched based on the harmonic 'load' is the solution. Individual capacitors, even if they are switched with the AC drive tend to produce overvoltages and even higher harmonics under certain cases. AC drive load power factor correction attempt is:unncecessary futile. Having said that there are devices installed at the motor end that contain capacitors among other components that do help with the mitigation of both harmonics and standing wave voltages. They are useful on AC drive rated motors and will save your standard, older motors. (Little known secret: you can also increase your cable length by about 30%. The AC drive manufacturers won't tell you this, but it is true.) Harmonics on the load side of an AC drives are generally high enough to warrant a reactor to be installed so as to protect a motor against overheating the harmonic currents cause. installing a capacitor there would suck all these harmonics currents, since the capacitor acts like the path of least resistance. hence them capacitors blow.