Motor cable influence on the converter fed AC motor drive conducted EMI emission

Investigation of common mode (CM) electromagnetic interference (EMI) currents in an AC motor drive fed by the pulse width modulated (PWM) voltage converter requires that parasitic capacitances existing in the converter, motor windings and feeding cable have to be taken into account. The motor voltage transients and related EMI emission are strongly correlated with resonance effects detectable in load circuits. The frequency impedance characteristics analysis allows to identify and determine resonance frequency ranges which are the foremost contribution for voltage ringing phenomena. The paper presents a method of analysis of AC motor windings parasitic capacitances with the particular account of cable influence on the broad-spectrum overall performance. The proposed circuit model allows for analysis of cable parameters effect on the conducted EMI emission of the AC motor drive.