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.

/pdf/a-review-of-traditional-helical-to-recent-miniaturized-jm17itasng.pdf

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

As one of the key components of aerospace power grid, the performance of on load tap changer (OLTC) of power transformer is very important. So it is necessary to realize real-time monitoring of its status. At present, there is no feasible monitoring scheme to carry out on-line monitoring and fault diagnosis for detecting faults of OLTC. The current waveform of the switching process will be abnormal due to the contact fault, the transition resistance fault, and most of the mechanical faults. This paper presents a fault diagnosis method for OLTC based on the current detection in the process of switching. Through on-line acquisition of current waveform in the switching process, empirical mode decomposition and Hilbert–Huang transform is used to calculate normalized time-frequency spectrum, and extract fault characteristic quantity, which can realize the comprehensive diagnosis of the running state of the equipment, and identify the early fault characteristics, and promote the process of the OLTC’s maintenance, from regular test to condition based maintenance. Experiment results prove that the designed fault diagnosis instrument can effectively monitor the working condition of OLTC during the switching process and make effective fault diagnosis.

A Fault Diagnosis Method for On Load Tap Changer of Aerospace Power Grid Based on the Current Detection

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

The invention discloses a short-time slowly-varying high-current measuring device based on a (printed circuit board) PCB type Rogowski coil, and the short-time slowly-varying high-current measuring device comprises the PCB type Rogowski coil, a sampling resistor and signal receiving equipment, wherein an inertialess link integrating circuit and a variable interval (VI) switching circuit are additionally and successively arranged between the PCB type Rogowski coil and the sampling resistor; and the PCB type Rogowski coil is a PCB type Rogowski coil which is provided with symmetrically arranged wires on two faces and is provided with return wires The short time slowly-varying high-current measuring device has the advantages that direct currents or low frequency high currents can be detected, the measuring bandwidth of the short time slowly-varying high-current measuring device can reach up to DC swung dash 200kHz, and the deficiencies of a conventional current sensor on the aspect of measurement of the direct currents or the low frequency high currents are eliminated; and since the PCB type Rogowski coil which is provided with the symmetrically arranged wires and is provided with the return wires is adopted by the short time slowly-varying high-current measuring device as a sensing head, complex electromagnetic interferences in a high-current system can be effectively eliminated, and a full-analog signal transmission manner is adopted by the device, so measurement errors can be effectively reduced

Short-time slowly-varying high-current measuring device based on (printed circuit board) PCB type Rogowski coil

The invention discloses a double-face symmetric wired printed circuit board (PCB) type Rogowski coil. The Rogowski coil comprises a PCB board, wherein the PCB board is provided with N internal diameter guide holes and N external diameter guide holes; the N internal diameter guide holes are uniformly distributed along the circumference of radius r; the N external diameter guide holes are uniformlydistributed along the circumference of radius R; the circumference of the radius r is concentric with the circumference of the radius R; wired copper foils penetrate through the N internal diameter guide holes and/or the N external diameter guide holes in turn and are symmetrically arranged on the two faces of the PCB board along the radius direction; a loop line ring is wound on a wired copper foil on one face of the PCB board; and the radius Rh of the loop line ring is greater than the radius R. The double-face symmetric wired PCB type Rogowski coil provided by the invention has the advantages of high parameter consistency, reproducibility and anti-interference capacity, guarantees a stable mutual inductance coefficient, can conveniently improve the accuracy, can be used as a current sensing head for current measurement under a complex electromagnetic environment, and is easy to produce in batches.

Double-face symmetric wired printed circuit board (PCB) type Rogowski coil

The invention discloses a method and device for eliminating mutual inductance coupling electromagnetic interference; the method of the invention comprises the steps that: after a current signal on thepower line of a strong current interference source system is detected and converted into a voltage signal, amplitude amplification is carried out to the normal phase or the reversed phase of the measuring conversion voltage signal and the voltage signal is converted into an output current signal, the value of which is not affected by the load; then the output current signal is converted into an offsetting signal which is equal to an interfering signal in amplitude and contrary to the interfering signal in phase; and the offsetting signal is injected into the loop of a weak current device to offset the interfering voltage inducted by the strong current interference source system to the loop of the weak current device by inductance coupling. The method of the invention dexterously brings ina voltage/current switching circuit, thereby overcoming the influence of the loop impedance of the weak current device on the offsetting effects and enlarging the application scope of the mutual inductance coupling offsetting method. The method and the device of the invention has low power consumption and cost, overcomes the defect that EMI filtering can not remove the interfering signals with the same frequency; compared with a shielding method, hardware devices required by the invention has smaller volume and lighter weight, thus not increasing the difficulty of system layout.

Method and device for eliminating mutual inductance coupling electromagnetic interference

A novel clasp PCB Rogowski coil with the symmetrical double-printed imprints and returning turn is proposed. The mutual-inductance between the coil and the primary conductor is precisely analyzed as the accuracy and sensitivity parameter. The calculation and measurement of mutual-inductance have been made under different disturbed conditions, including the position error of the primary conductor, the existence of external interference currents. The results indicate the clasp PCB Rogowski coil is good in compatibility, accurate and steady in mutual-inductance.

Tao Tao

Papers

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

Short-time slowly-varying high-current measuring device based on (printed circuit board) PCB type Rogowski coil

Double-face symmetric wired printed circuit board (PCB) type Rogowski coil

Method and device for eliminating mutual inductance coupling electromagnetic interference

Precise Mutual-Inductance Analysis of a Novel Clasp Rogowski Coil with Symmetrical Double-Printed Imprints