Mixed-Mode Effect on Motor Common Mode Current

This paper presents the mixed-mode effect on motor common mode current (CMC) in an adjustable speed drive (ASD). It is expected that the motor CMC is lower than inverter output CMC. However, the measurement result of the ASD shows that the AC motor input CMC is higher than the inverter output CMC in a frequency range. By using a mixed-mode (MM) 6-port networks, it is proven that the AC motor input CMC is higher due to an MM CMC which is generated from differential mode current.