Line current harmonics of VSI-fed adjustable speed drives

Voltage source inverter (VSI)-fed adjustable speed drives are frequently used in energy saving applications like the speed regulation of pumps and fans. The power supply of the inverter consists of a diode rectifier feeding a large DC link capacitor. Thus, very high line current harmonics occur if no inductance is provided for current smoothing. Assuming AC choke inductance, this paper presents diagrams in order to predetermine easily the harmonic distortions of the line current. The parameters considered are AC reactance, DC capacitor and the actual drive loading. With this, a more detailed description of the injected current harmonics of VSI-fed drives is achieved in order to improve the accuracy of harmonic analysis purposes. Examples show the use of the proposed method and comparing measurements proves its validity in practical applications.