Filters for Active Front End Motor Drives

Present day IGBT based power adjustable speed drives have fast turn-ON and turn-OFF times results in high dv/dt being applied to the motor terminals. The high dv/dt switching waveforms along with travelling wave effects of long cables stress motor insulation, cause high ground currents and affects the motor bearings. These issues are exacerbated in PWM Active Front End (AFE) rectifier based motor drives when compared to one using a diode rectifier. This paper briefly outlines problem associated with IGBT technology based ASD with AFE rectifier using long cables. The common mode voltage due to such motor drive with AFE rectifier is analysed. An integrated approach for filter design is discussed wherein the adverse effects of both AFE rectifier and the drive inverter are addressed on both common and differential mode basis. The proposed topology address the problems of common mode voltage, common mode current and voltage doubling due to ASD. The design procedure for this proposed filter topology is discussed with experimental results that validate the effectiveness of the filter.