In-Circuit Characterization of Common-Mode Chokes

The two current probes measurement method was employed by other researchers to measure the radio-frequency impedance of AC power mains. In this paper, with a modified measurement setup, the method is extended to measure the common-mode (CM) impedance of a CM choke under in-circuit condition. With a premeasurement characterization process, the effect of the measurement setup can be determined and eliminated. The proposed measurement provides a more realistic assessment of the CM impedance characteristic of any CM choke under actual operating condition.