Eddy-Current Effect in Shielded Rogowski Coil for Power Electronic Applications: Mechanism, Essence, and Countermeasure

With next-generation wide-bandgap (WBG) power devices achieving faster switching speeds and higher d<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</i>/d<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i>, high-bandwidth shielded Rogowski coil (RC) is being actively explored to accurately capture rapid current transients while effectively suppressing external common-mode interference induced by d<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</i>/d<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i>. However, eddy-current effect inevitably parasitizes the external shielding of the shielded RC, resulting in significant variations in its forward gain characteristics. This paper first investigates the pivotal role of external shielding in achieving high bandwidth and interference immunity in RC design, while also highlighting the inevitability of eddy-current effect within it. Following this, an in-depth analysis of the mechanism underlying eddy-current effect is presented, providing theoretical insights into the characteristic degradation of the shielded RC's forward gain, which follows a characteristic inductive-resistive-inductive response. Building on this foundation, the study further elucidates the physical essence of these behaviors: in the mid-frequency range, resistive behavior is mainly driven by the eddy-current loss induced by the parasitic resistance of the external shielding, whereas in the high-frequency range, inductive characteristics are predominantly influenced by the field distortion resulting from external shielding degradation. Finally, a countermeasure is proposed to establish a corresponding capacitive-resistive-capacitive response by leveraging the inherent dual-transition characteristics of a “passive + active” integrator. This method enables the shielded RC to maintain a flat system gain across a broad frequency range (not less than 100 MHz) without altering circuit setup, increasing system complexity, or requiring cumbersome implementation. Extensive comparative experiments in both the frequency and time domains validate the accuracy of the established eddy-current model and confirm the effectiveness of the proposed compensation methodology.