Near-Magnetic Interference in Rogowski Coil for Power Electronic Applications: Mechanism and Mitigation

Rogowski coil (RC), valued for its high bandwidth, galvanic isolation, and ease of integration, is widely employed in high-speed integrated power electronics. However, near-magnetic interference (NMI) arising from inductive coupling with adjacent current sources is often underestimated, which undermines the RC's robustness in crucial applications such as characterization, protection, and control. This paper first reveals the inevitability of NMI in RCs. Building upon this, the mutual inductance equation between the RC and external interference sources is derived in detail, establishing a solid theoretical foundation for efficient and quantitative interference evaluation. The derivation methodology is further generalized to arbitrary points in space, allowing for the quantitative analysis of the effect when the circuit under test (CUT) is offset from the RC's center. Theoretical analysis highlights the number of turns as a key factor, demonstrating that appropriately increasing it can effectively mitigate the influence of both external NMI and internal CUT eccentricity. The inherent design trade-off between measurement bandwidth and interference immunity is further analyzed. Design guidelines for establishing the upper and lower limits of the number of turns are derived, and the differential mode rejection ratio (DMRR) is introduced as an intuitive metric to quantify the interference suppression capability. The accuracy of the proposed NMI model and the effectiveness of mitigation strategies are corroborated by Ansys Q3D simulations and extensive frequency- and time-domain experiments.