The Rogowski coil is an old device for current measurement. It has been modified and improved over a century and is still being studied for new applications. The Rogowski coil has various advantages over conventional magnetic current transformers (CTs). Not only can it be used instead of CT, but also it has various utilizations in other fields. This paper provides a brief review on different aspects of the Rogowski coil and its advancement procedure, during last decades. In this paper, the history of the coil is brifely reviewed and its bases and applications are discussed. The Rogowski coil is analyzed from different points of view, including different integration techniques in the output stage, models for the Rogowski coil, experimental methods for parameter measurement in models, and method for determining the damping resistor. Finally, a brief review over different applications of the coil ends this paper.

The Rogowski Coil Principles and Applications: A Review

Silicon-carbide (SiC) transistors with growing readiness for the power converter market have raised an emerging need for high-performance gate driver (GD) units to maximize their remarkable characteristics. In particular, the GD units for the SiC devices that experience extremely fast commutations at the medium-voltage level require powerful driving capability, effective short-circuit (SC) protection, and superb common-mode transient immunity. Thereby, this article presents a systematic enhanced GD (eGD) solution that incorporates three scalable features compatible with almost all the SiC mosfet modules. First, a BJT-based multicell current booster is proposed to attain balanced high driving current, low losses, gate-loop inductance less than 1 nH, and great cross-talk immunity. Second, a nonintrusive Rogowski switch-current sensor with high bandwidth and fair accuracy is developed, capable of detecting SC fault in 86 ns and softly turning off 5 kA SC current in 1  $\mu$ s. Third, two noise-free isolation architectures are proposed to mitigate common-mode noise-admittance by more than 100 dB. Fundamentals, analytical designs, experimental validations, and scalability discussions of the three techniques are elaborated, respectively. Finally, a 6-kV, 84-A, and 102-V/ns continuous pump-back test is demonstrated, for the first time, to verify the eGD's excellent performance.

High-Scalability Enhanced Gate Drivers for SiC MOSFET Modules With Transient Immunity Beyond 100 V/ns

Latest wide-bandgap power devices are switching progressively faster compared with existing silicon devices. Their accurate current measurements for either control or protection have therefore become tougher. One method that can fulfill the requirements is to use a Rogowski coil and its accompanied electronics to form a Rogowski current sensor with high bandwidth, small volume, low cost, and ease of integration. This article therefore aims to review various aspects of the Rogowski current sensor from its history, measuring principles to modern power-electronic applications. The applications have, in turn, motivated a progression from traditional helical to recent miniaturized printed circuit board implementation, in order to improve the overall power density. This progression has similarly been reviewed, together with its various design aspects applied to the winding, integrator, shielding, and parameters of the Rogowski current sensor. Future challenges and directions are then summarized, whose ultimate goal is to maximize accuracy over a wide bandwidth without being affected by radiated and near-field-coupling interferences.

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A Review of Traditional Helical to Recent Miniaturized Printed Circuit Board Rogowski Coils for Power-Electronic Applications

In this paper, a resonant damping circuit to suppress the switching ringing of full SiC mosfet is proposed. It reveals that the ringing phenomenon caused by parasitic impedances of switching circuit can be damped out using air core PCB transformer which has a properly designed secondary side circuit. The design method for PCB transformer and the secondary circuit are developed considering the physical dimension applied to the PCB transformer inserted between full SiC mosfet module and snubber capacitor. Experimental results using 1200 V–180 A full SiC mosfet module validate the design method and the performance of the proposed air core PCB circuit. Thanks to the damping circuit, the resonant component due to the switching ringing has been reduced to a half compared to that of system without damping circuit.

A Damping Scheme for Switching Ringing of Full SiC MOSFET by Air Core PCB Circuit

A time-domain model of the analog adaptive interference cancellation system (AAICS) involving both the interference and the desired signal is proposed. The stability, interference cancellation ratio, and convergence time of the AAICS are analyzed in detail. In addition, the desired signal cancellation ratio is taken into account in order to evaluate the system performance and optimize the AAICS more accurately. It is found that the parameters including the loop gain and the time constant of the negative feedback control loop need to be set reasonably so as to reduce a great distortion to the desired signal. The rules of parameter optimization are obtained for the AAICS operating in high frequency. Experiments are carried out to demonstrate the system's performance varying with parameters, and experimental results are in agreement with theoretical analysis, which is of great value for the optimization design of the AAICS.

Performance Analysis and Optimal Design of the Adaptive Interference Cancellation System

Rogowski coil is used as a current transducer in complex electromagnetic environment, whose anti-interference property bears on the accuracy of the current measurement. Based on the ordinal straight-coupled foils of the current PCB Rogowski coil, this paper proposes a newly designed PCB Rogowski coil with symmetrical double-printed imprints and returning turn to gain better precision and performance. The mutual inductance between the coil and the primary conductor is chosen as the sensitivity parameter to contrastively analyze the anti-interference property of three coils, including the ordinary straight-coupled coil, the symmetrically printed coil with or without returning turn. The calculation and measurement of mutual inductance have been made under different disturbed conditions, such as the eccentricity from axis of the primary conductor and the influence of external parallel and perpendicular currents. The results indicate that the newly designed PCB Rogowski coil with symmetric imprints and returning turn is good in compatibility, strong in anti-interference property, and also accurate and steady in mutual inductance. Therefore, it is suitably applied as the sensing head of current measurement in the complex stray electromagnetic fields.

Design of PCB Rogowski Coil and Analysis of Anti-interference Property

As a natural result of the electrified integration and electrical energy revolution, the electromagnetic launch (EML) technology will be inevitably used for future launch missions. This paper has summarized research focuses in this field according to the published papers on EML in China during the past decade and mainly introduced the current research and progress in several key technologies, including launcher, integrated launch package, high-power high-density supply, and overall control/maintenance. Some common pressing problems are pointed out to provide direction for the application of EML technology in engineering and many other fields, such as launcher life, miniaturization of power supply, and improvement of energy availability.

Research Progress of Electromagnetic Launch Technology

This paper investigates the influence of non quadrature of phase shifter to the convergence characteristic and interference cancellation ratio (ICR) of a Single chunnel analog adaptive interference cancellation system (SAAICS). We established the analysis model and solved the transient and steady-state characteristics of weights. Through the analysis of steady-state error and ICR, we obtained the rule of ICR variation with quadrature offset angle. And that rule with different interference signal phase was gained. The non quadrature of phase shifter decreases the average convergence speed. The more quadrature offset is, the low average convergence speed will be. But the ICR does not decrease absolutely with the increase of quadrature offset. It is related with the interference signal phase. For different interference signal phase, the rules of ICR variation with different quadrature offset angles are nearly consistent. The analyses are in agreement with the computer simulation. For non quadrature of phase shifter, the system is time-variant. When the signal frequency is higher, the influence of the time-variation is smaller.

Influence of Non Quadrature of Phase Shifter to Adaptive Interference Cancellation System

Static longitudinal end effect caused by truncated iron and coil windings is the inherent characteristic of linear motors. For multisegment long primary double-sided linear induction motors (DLIMs), subsection power supply mode results in longer iron than excited coil windings, which aggravates the static longitudinal end effect. First, the characteristics of the DLIM impedance matrix are researched through experiments. The impedance matrix is calculated by the measured amplitude and phase of the three-phase voltage and current. Unlike the traditional rotating induction motor, the matrix of DLIM is not a traditional cyclic symmetric matrix. Positive-sequence impedance, which is defined and obtained based on the impedance matrix, could be used to measure parameters by open-circuit and short-circuit experiments. The parameters measurement method is validated more accurate than the traditional average phase impedance. The research results, which are validated by test data from the long primary DLIM system capable of producing 400 kN of force, operating at the 100-MW peak power level, could be the reference for accurate description of the dynamics motor model and parameter measurement.

Impedance Matrix and Parameters Measurement Research for Long Primary Double-Sided Linear Induction Motor

This paper investigates the correlation-integrator, correlation-lowpass and correlation-proportion control methods of an adaptive interference cancellation system (AICS). For a single chunnel AICS, the convergence characteristic of different control methods is gained and contrasted. The different functions of using active lowpass and passive lowpass are analyzed. The formulation of the changes of interference cancellation ratio (ICR) and convergence time with the change of interference signal is calculated. Under the correlation-integrator control, the optimum weights can be gained and the residual error is zero. With the correlation-lowpass control and correlation-proportion control, the steady-state weights differ from the optimum weights, so the residual error is not zero. Active lowpass has more advantages for increasing ICR and convergence speed than passive lowpass. The more interference signal decreases, the lower ICR is for lowpass and proportion control and the longer time converging to steady-state will be for all the control methods. If we limit a convergence time as a standard, the ratio of the convergence time to the limiting time is a quadratic function of the reduce times of the interference signal.

Weiming Ma

Papers

Design of PCB Rogowski Coil and Analysis of Anti-interference Property

Research Progress of Electromagnetic Launch Technology

Influence of Non Quadrature of Phase Shifter to Adaptive Interference Cancellation System

Impedance Matrix and Parameters Measurement Research for Long Primary Double-Sided Linear Induction Motor

Adaptive Interference Cancellation System with Different Correlation Control Methods