Printed Circuit Board Rogowski Coil Research Articles

A Differential Compensated Air Coil Current Sensor for Switching Current Measurement of Power Devices

Accurate current measurement is the basis for power devices to achieve switching characteristics evaluation, real-time control, reliability diagnosis, life prediction, etc. With the rapid development of power semiconductor device technology, requirements for current measurement are getting more and more stringent. The printed circuit board Rogowski coil current sensor (PCB RCCS) is a potential competitor, which has excellent bandwidth and integrability. However, the contradiction of the droop and drift phenomena as one of the main challenges restricts the employ of the RCCS in switching current measurements. In this paper, a differential compensation scheme that can solve these problems simultaneously with a lower error and cost is proposed. And the sensitivity and bandwidth of this sensor can be accurately obtained. Finally, a buck and single-phase full-bridge inverter experimental platform are built to verify the effectiveness of the PCB RCCS in the measurement of the switching current and inductor current, respectively.

Design of PCB Rogowski Coil Current Sensor With Low Droop Distortion

Wide bandgap devices (SiC and GaN) bring the potential for a great increase in power density of power electronics, but also pose a challenge to the bandwidth of the current sensor because of the high operating frequency. Rogowski coil is suitable for high-frequency current measurement due to its characteristic of differential output, but the existing design is difficult to take into account the sensitivity and mutual inductance at the same time, and faces the inherent defect of droop distortion. This article proposes an optimal printed circuit board (PCB) Rogowski coil structure design method for SiC MOSFET power module and a novel sample-filter-hold (SFH) method to minimize droop distortion in integrators. First, the optimal parameters with multiobjective constrained optimization of the Rogowski coil current sensor for the SiC-MOSFET power module are obtained. Then, the influence factors of droop distortion of the sensor in buck converters and inverters are quantitatively analyzed for the first time and an SFH suppression method is proposed, which can eliminate the offset caused by droop distortion reliably and accurately. Finally, the experimental results demonstrate that the proposed Rogowski coil design method and the SFH method for lower droop distortion achieve better low-frequency performance compared to the commercial Rogowski coil.

Current Measurement Method of Multiple Chips Using Rectangular PCB Rogowski Coils Integrated in Press Pack IGBT Device

Unbalance of transient currents of multiple chips inside press-pack insulated-gate bipolar transistor (PP IGBT) results in degrading operation and even device damage. Chip currents measurement plays an essential role to understand and solve this problem. Printed-circuit board Rogowski coil (PCB RC), as a small, noninvasive, and high bandwidth current sensor, is very suitable for this application. However, PCB RC integrated with multiple Rogowski coils (RCs) is still difficult to be applied to measure the current of multiple chips in press pack IGBT device because of the low measurement accuracy due to the large interference. In this letter, a high accuracy PCB RC with ten rectangular RCs inside PP IGBT is proposed to measure ten chip currents at the same time. Different from single RC measuring single chip current, the interference of adjacent chip currents has to be considered, and is reduced to 0.6% by optimizing the turns arrangement and lead wires of RCs. The noise of cross talk of adjacent RCs is 1.7% by decreasing the capacitance coupling between RCs. Shielding layers and grounding patter of lead wires for ten RCs are proposed to eliminate the interference of collector voltage. The experiment of transient process of ten chips verifies the effectiveness of proposed PCB RC, and measurement error is only 1.8%.

An Active Gate Driver of SiC MOSFET Module Based on PCB Rogowski Coil for Optimizing Tradeoff Between Overshoot and Switching Loss

The superior characteristics of the silicon carbide metal-oxide-semiconductor field-effect transistor (SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> ) allow its wide use for improving the efficiency and power density of power electronic systems. However, the higher switching speed exacerbates the problems of overshoot, oscillation, and electromagnetic interference (EMI), which need to be properly addressed. In this article, a novel stage-detection closed-loop active gate driver (AGD) based on the printed-circuit-board (PCB) Rogowski Coil is proposed for optimizing the switching performance of SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s. And its stage identification threshold design can weaken the influence of the varying nonlinear parameters, especially for the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> process. First, the gate driver trajectory and the switching process of the SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> are analyzed. The optimal driver parameter dynamic configuration among the existing stage-control schemes is defined and unified, which aims to optimize the tradeoff between the overshoot and switching loss. Then, the parameter design of the PCB Rogowski Coil is illustrated. And the operation principle and working process of the proposed AGD are introduced. Finally, the performance of the proposed AGD and the effectiveness of the stage-control schemes are verified in the double-pulse test under different conditions. The experimental results show that the proposed AGD can not only reduce the overshoot and suppress the oscillation but also optimize the compromise of the switching loss and switching time.

Development of Detachable Rogowski Coil Current Sensor using PCB for High Voltage Cable Partial Discharge Measurement

Insulation failure in High Voltage (HV) cables is evaluated using a variety of monitoring techniques. Previous silicon technologies were outperformed by wide-bandgap semiconductor power devices with faster switching speeds. Their precise current management or current protection measures must be upgraded. As a result, their precise current control or protection measures have become more sophisticated. The traditional Rogowski Coil (RC) with the magnetic core, on the other hand, has low measurement accuracy, a short measuring range, and is difficult to fabricate. This paper presents and discusses the development of a Rogowski Coil using a detachable Printed Circuit Board (PCB) as a current sensor for Partial Discharge (PD) measurement. Furthermore, the development of this innovative current sensor concentrated on the detachable PCB Rogowski Coil’s capability to measure as a high-voltage (HV) current sensor and its sensitivity in fault diagnosis, over-voltage current sensing, and high-impulse current sensing on HV cables. The experimental design, techniques, and measurement parameters used in models were discussed. Finally, a brief analysis of the detachable PCB RC current sensor such as sensitivity, maximum voltage and current detection is presented. This paper can also be used as a guideline for other researchers to develop an advanced RC current sensor using PCB as a HV current sensor in the future. The measurement results of the detachable PCB RC current sensor such as the sensitivity and current detection signal can also be used as a guideline by another researcher. As a result, the goal of this project is to measure PD on HV cables using an RC current sensor by utilising PCB technology.

Designing and manufacturing of electric arc furnace currents measurement system in Mobarakeh Steel Company by printed circuit board‐type Rogowski coils

This paper deals with the utilization of printed circuit board Rogowski coils (PCBRCs) for differential protection of electric arc furnace (EAF) transformers in Mobarakeh Steel Company (MSC), Isfahan, Iran. Because of a high level of current (in the range of 100 kA) in the EAF transformers in the MSC, employment of differential protection is quite challenging. Conventional current transformers (CTs) cannot offer reliable performance for very high current levels. The PCBRCs are a branch of Rogowski coils (RCs) that can be manufactured with high precision using computer-aided design approaches and have the capability for the measurement of very large currents. In this study, we have designed and manufactured two sets of PCBRCs to measure current in the primary and secondary sides of the EAF's transformers in the MSC. The PCBRCs are followed by a signal condition circuit (SCC) which includes a low-pass filter, amplifier, and voltage-to-current (V-to-I) converter block. Thanks to the SCC, the high current of the transformers can be properly sensed and transmitted over a long cable that connects the PCBRCs to the relay. Furthermore, a novel model is suggested for the EAF that includes characteristics of both time and frequency domain models. The suggested model is developed using a large number of recorded data from the MSC and can model the non-linear and time-variant behaviours of the EAF. The proposed PCBRCs, SCC, and EAF modelling are evaluated by some simulations and experiments in the MSC.

Design of Open-Ended Structure Wideband PCB Rogowski Coil Based on New Winding Method

Compared with the traditional Rogowski coil, printed circuit board (PCB) Rogowski coil has the advantages of high measurement accuracy, simple manufacturing process and low cost. It has become an important device in current measurement. However, the existing PCB Rogowski coils are mostly closed, and the open-ended structure PCB Rogowski coils are susceptible to external magnetic field interference. This paper proposes an open-ended structure PCB Rogowski coil based on a new winding method, so that the two open-ended PCB Rogowski coils are evenly distributed when closed, while improving the coil’s immunity to external magnetic fields based on the winding method of equal area of the de-wired and loop. In addition, this paper uses the hybrid integration circuit and the back-end matching method to achieve the broadband measurement performance of the sensor. Finally, the experimental results show that the mutual inductance difference between the closed and open-ended structure PCB Rogowski coil is less than 0.5% under the same wiring mode. Under the equivalent current interference at 50 mm from the measured current, the maximum interference coefficient of the open-ended structure coil is 1.45%; in sine sweep and pulse current test conditions, the frequency band is 34 Hz–3.5 MHz.

Method of Segmented Turns Arrangement of PCB Rogowski Coil With Anti-Interference Ability

The printed circuit board Rogowski coil (PCB RC) has been widely applied in the complex electromagnetic environment, such as power electronic devices, where it is placed outside but very close to current-carrying conductors; thus, this brings great challenges to the anti-interference ability of it. Generally, the anti-interference ability of PCB RC is greater with more turns; however, the number of turns is limited by two aspects: the one is the bandwidth of PCB RC, which is reduced as the turns increase, and the other is the minimum distance between vias, which is determined by process technology. This article proposed a method of segmented turns arrangement of PCB RC to acquire better anti-interference ability almost without lowering the bandwidth and get closer to the technical limit of distance between vias. The segmented turns are designed to be stair-stepping rather than rectangular used in traditional integral turns, which is equivalent to splitting a complete rectangular turn into several small rectangular turns so that the turns density is increased with the anti-interference ability improved. As an example of the method, a square PCB RC with proposed segmented turns is designed and compared with the PCB RC with traditional integral turns, and the results of calculation and experiment show that the anti-interference ability of PCB RC with proposed segmented turns is enhanced to be doubled and very great even near the corner of the PCB RC.

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

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.

PCB-Based Current Sensor Design for Sensing Switch Current of a Nonmodular GaN Power Semiconductor

GaN-based power semiconductors exhibit small on-resistance and high dv/dt of the switch characteristics, thereby enabling the construction of high-efficiency, high-density semiconductor systems with fast switching and low power loss characteristics and miniaturization of passive devices. However, owing to the characteristics of GaN devices that result in them being significantly faster than other devices, the accuracy of the switching transient response significantly affects the noise or inductance in the device. Therefore, securing sufficient sensor bandwidth is considerably important for accurate current measurement in GaN-based devices. Conversely, the current sensor in the form of a non-insulated coil must secure sufficient bandwidth and overcome the tradeoff relationship with measurement sensitivity; moreover, the sensor configuration must be applicable to various power semiconductor types. This study proposes a current sensor model that applies the principle of the printed circuit board Rogowski coil to a surface mount device-type GaN-based half-bridge structure. This structure is applicable to a nonmodular power converter and is designed to secure sufficient bandwidth with a minimum area while simultaneously exhibiting high sensitivity. For the coil design, mutual inductances with existing coil structures were compared and analyzed, and the frequency response and magnetic analysis were evaluated. Experimental verification was performed and the transient response characteristics in various DC voltage ranges are discussed.

Integrated Rogowski Coil Sensor for Press-Pack Insulated Gate Bipolar Transistor Chips.

Recently, the press-pack insulated gate bipolar transistor (IGBT) has usually been used in direct current (DC) transmission. The press-pack IGBT (PPI) adopts a parallel layout of boss chips, and the currents of each chip will be uneven in the process of turning on and off, which will affect the reliability of the device. To measure the currents of each chip, based on the analysis of the principle and equivalent model of the Rogowski coil, this paper puts forward the design scheme and design index of multi-layer printed circuit board (PCB) Rogowski coil with good high-frequency performance, strong anti-interference ability and sufficient sensitivity. With the simulation analysis of Altium Designer and ANSYS softwares, a 1 mm thick, 76-turn integrated four-layer PCB Rogowski coil is designed. Then, adding a composite integrator, an integrated Rogowski coil sensor for measurement of PPI chips currents is designed. The Pspice simulation and the experiment results show that the sensor is fully satisfied with the chip current measurement.

Structure and modelling of four‐layer screen‐returned PCB Rogowski coil with very few turns for high‐bandwidth SiC current measurement

Accurate measurement of current through a silicon carbide (SiC) device is especially challenging, because of its fast switching speed. Its accompanied current sensor must hence have a high-bandwidth and a high-noise immunity. It must also not interfere with operation of the device. Due to these, the printed-circuit-board (PCB) Rogowski current sensor is particularly suitable, but normally requires many layers. With only four layers, the existing Rogowski coils are not yet capable of shielding ambient voltage and magnetic noises simultaneously. Moreover, their computed and measured self-inductances are usually very different with errors as high as 45% reported in the literature. To resolve these issues, an alternative four-layer screen-returned PCB coil has been presented. The described coil uses very few turns to preserve its high bandwidth at the expense of even tougher determination of its self-inductance. An alternative piecewise modelling method has therefore been proposed for finding its self-inductance, needed for designing its theoretical bandwidth. These, together with a non-inverting integrator, permit current through an SiC device to be measured accurately, as demonstrated experimentally.

Research on Small Square PCB Rogowski Coil Measuring Transient Current in the Power Electronics Devices.

With the development of China’s electric power, power electronics devices such as insulated-gate bipolar transistors (IGBTs) have been widely used in the field of high voltages and large currents. However, the currents in these power electronic devices are transient. For example, the uneven currents and internal chip currents overshoot, which may occur when turning on and off, and could have a great impact on the device. In order to study the reliability of these power electronics devices, this paper proposes a miniature printed circuit board (PCB) Rogowski coil that measures the current of these power electronics devices without changing their internal structures, which provides a reference for the subsequent reliability of their designs.

Extraction of Junction Temperature of SiC MOSFET Module Based on Turn-On dIDS/dt

In this paper, a method of extracting the junction temperature based on the turn-on current switching rate (dIDS/dt) of silicon carbide (SiC) metal-oxide semiconductor field effect transistors (MOSFETs) is proposed. The temperature dependence of dIDS/dt is analyzed theoretically, and experimentally to show that dIDS/dt increases with the rising junction temperature. In addition, other factors affecting dIDS/dt are also discussed by using the fundamental device physics equations and experiments. The result shows that the increase of the DC-link voltage VDC, the external gate resistance RG-ext, and the decrease of the driving voltage VGG can increase the temperature sensitivity of the dIDS/dt. A PCB (printed circuit board) Rogowski coil measuring circuit based on the fact that the SiC MOSFET chip temperature and dIDS/dt is estimated in a linear way is designed to obtain the junction temperature. The experimental results demonstrate that the proposed junction temperature extracting is effective.

Micro PCB Rogowski coil for current monitoring and protection of high voltage power modules

We have developed a printed circuit board Rogowski coil for monitoring of current and protection of high-voltage power modules and packages. It is small, thin, and inexpensive current sensor and is almost the ideal Rogowski coil because of its fishbone pattern. For noise reduction under high-voltage/-current conditions in a module, shield layers and coaxial connector are employed. In addition, a new, fast simulation tool was developed to optimize the main coil pattern for realization of arbitrary printed circuit board geometry in specific, limited spaces.

Switch fault diagnosis and capacitor lifetime monitoring technique for DC–DC converters using a single sensor

Owing to the key role of the power electronic converters in various applications, their reliability is an important issue. The electrolytic capacitor and the power switch are the most vulnerable components of the converters. On fault occurrence in these components, a suitable remedial strategy should be employed to prevent further damages. The first step in any remedial strategy is fault diagnosis including fault detection and identification. This study proposes a technique for switch fault diagnosis and capacitor lifetime monitoring in non-isolated single-switch DC–DC converters. The proposed cost-effective method could be easily implemented using a printed circuit board Rogowski coil (PCBRC) on the capacitor terminals. The derivative of the capacitor current is captured by the PCBRC. The captured signal contains suitable signatures for detection of switch open-circuit and short-circuit faults. In addition to switch fault detection, lifetime of the converter capacitor is also monitored by the PCBRC via calculation of the capacitor equivalent series resistance. The proposed technique is implemented for a buck converter. The experimental results confirm the capability of the proposed technique for switch fault diagnosis and capacitor lifetime monitoring in non-isolated single-switch DC–DC converters.

A Novel Transient Fault Current Sensor Based on the PCB Rogowski Coil for Overhead Transmission Lines

The accurate detection of high-frequency transient fault currents in overhead transmission lines is the basis of malfunction detection and diagnosis. This paper proposes a novel differential winding printed circuit board (PCB) Rogowski coil for the detection of transient fault currents in overhead transmission lines. The interference mechanism of the sensor surrounding the overhead transmission line is analyzed and the guideline for the interference elimination is obtained, and then a differential winding printed circuit board (PCB) Rogowski coil is proposed, where the branch and return line of the PCB coil were designed to be strictly symmetrical by using a joining structure of two semi-rings and collinear twisted pair differential windings in each semi-ring. A serial test is conducted, including the frequency response, linearity, and anti-interference performance as well as a comparison with commercial sensors. Results show that a PCB Rogowski coil has good linearity and resistance to various external magnetic field interferences, thus enabling it to be widely applied in fault-current-collecting devices.

Hybrid PCB Rogowski Coil for Measurement of Nanosecond-Risetime Pulsed Current

Self-integrating Rogowski coil has been widely used for measurements of pulsed currents from nanosecond timescale to microsecond timescale in pulsed power systems. Appropriate designs of coil’s structure are vital to high-frequency response. This paper proposed a new structure of Rogowski coil so as to provide a better response to fast pulsed current. Four Rogowski coils with different structures were tested in three different platforms. Experimental results showed that the hybrid Printed Circuit Board Rogowski coil had the best performance in this paper, which could respond to square waves with fronts of $\sim 2$ ns and had a sensitivity of 0.585 V/kA. The designed maximal peak current was 100 kA.

Application of Rogowski Search Coil for Stator Fault Diagnosis in Electrical Machines

A high precision Rogowski search coil (RSC) is proposed for monitoring of rotating electrical machines. The RSC includes several sets of printed circuit board Rogowski coil, in which any set includes two printed circuit boards with imprinted coils located adjacent to each other. The RSC offers a number of advantages including compact size, great accuracy, high bandwidth, low cost, and it is applicable even for already fabricated electric machine. Performance of the RSC is evaluated by some experiments.

Gate Unit With Improved Short-Circuit Detection and Turn-Off Capability for 4.5-kV Press-Pack IGBTs Operated at 4-kA Pulse Current

This paper presents a gate unit with short-circuit protection for a 4.5-kV press-pack insulated gate bipolar transistor (IGBT) designed for pulsed applications and operated at a pulse current of 4 kA and the results of short-circuit tests performed with the mentioned switch and the gate unit. Initially, an overview of the gate unit, the implemented gate boosting as well as the two-stage turn-off and active clamping is given. An over- di/dt as well as an over-current detection using a printed circuit board (PCB) Rogowski coil is used in the gate drive to protect the IGBT during operation. Then, the design of the PCB Rogowski coil is introduced including partial element equivalent circuit simulations to predict the coil parameters. Measurements were made to verify these simulations. Afterward, two types of short-circuit tests were performed. First, the over- di/dt detection was tested by turn-on into a short circuit. The tests show that the over- di/dt detection reacts very fast. The IGBT was always able to turn off the short-circuit current. The maximum short-circuit current was 4.4 kA. Second, tests using an auxiliary switch were made to investigate the short-circuit events during pulse top. The IGBT was able to turn off a maximum short-circuit current of 8.7 kA.