Common-mode choke coils characterization

Common-mode (CM) chokes are four-terminal devices with different CM and differential-mode (DM) characteristics. The paper reviews the models for two- and four-terminal inductors and presents two methods to obtain the CM and DM characteristics of four-terminal devices. More specifically, it shows how the insertion loss and pi-equivalent circuits of a CM choke can be obtained using two- and four-port network parameters. However, these characterization methods are applicable not only to CM chokes, but to any four-terminal component or network, such as single-phase power filters. The results show that second order linear circuit models cannot describe accurately the CM and DM characteristics of a CM choke over a wide frequency range. For the studied example, the DM characteristics were more complex than the CM ones.