Common Mode and Differential Mode Analysis of Three Phase Cables for PWM AC Drives

This paper proposes a new 3-phase transmission line model with the first successful use of 2D finite element analysis (FEA) to extract and predict cable R-L-C parameters over a wide range of frequencies. The significance is that the FEA methodology to extract high frequency parameters were shown to be accurate and eliminates costly cable testing. The 3-phase FEA parameters can also be transformed for use with historical single-line transmission line models. The FEA approach allows unsymmetrical cables to be studied in a 3-phase cable-drive and motor simulation setting. FEA predicted vs. measured R-L-C parameters as function of frequency was within 5-10%. A 3-phase drive-cable-motor power electronic simulator program using predicted FEA parameters to predict CM current and DM motor overshoot (ringing) voltage was found to be within 7-15% of measured waveforms from 10 ft to 1000 ft cable length variation for two different cable type configurations. Analysis provided is also applicable to power system transient studies on AC line connected equipment