  The in-circuit common-mode (CM) impedance at the AC input of a motor drive
system (MDS) provides valuable inputs for evaluating and estimating the CM
electromagnetic interference (EMI) noise generated by the switching of power
semiconductor devices in the MDS. This paper introduces a single-probe setup
(SPS) with frequency-domain measurement to extract the in-circuit CM impedance
of a MDS under its different operating modes. The SPS has the merits of
non-contact measurement and simple structure.
