Cable and Motor Winding Impedance Interactions in Motor Drive Systems and its Impact on HF Overvoltages

Voltage stress across motor winding is critical for insulation health when its series resonance frequencies, which have the least impedances, known as antiresonances, coincide with overvoltage (OV) resonance frequencies across it, named as antiresonance phenomenon (ARP). First, this article discloses that the OV resonance frequencies across motor winding (load) can be represented by the combination impedance of cable plus load. Second, it investigates the interactions between the cable and load impedances in different layouts and examines their impact on the ARP. Then, it discloses the sensitivity of ARP versus cable and load impedance parameters. Lastly, the ARP's correlation with these parameters establishes a safe operation area as a motor drive system design guideline. Contrary to the general belief that systems using short cable or integrated systems have less insulation damage, this study shows that the OV stress in these systems can be critical. This article offers a simplified methodology to optimize the reliability of the drive system and mitigate the ARP. By using this approach, the article suggests that the time-consuming iterative design of dV/dt filters or overdesign of insulation can be eliminated. The practical test and modeled system are conducted to validate the approach.