Fixture Compensation Strategy for Impedance Characterization of Single-Phase Chokes Used in Power Electronics Applications

Differential-mode (DM) chokes and single-phase common-mode (CM) chokes have been widely adopted in singe-phase power electronics systems to mitigate the electromagnetic interference (EMI). For optimal filtering design and component selection, high-precision and broadband impedance information of them provide useful insights. To characterize these chokes, measurement methods are straightforward, requiring a fixture for connecting the measurement apparatus with choke leaded terminals. Obviously, this will introduce parasitic parameters into the measurement setup, ultimately affecting accuracy. This article proposes a fixture compensation strategy to address this issue. By regarding the fixture as a black box, its parasitic effect can be compensated via the network analysis concept. Through the experiments, the effectiveness of the proposed strategy has been validated, realizing good accuracy across frequencies from 150 kHz to 120 MHz, which covers most of the conducted EMI standards, such as CISPR-25.