Electromagnetic Interference Levels Research Articles

Real-Time Monitoring of Temperature Rises of Energized Transformer Cores With Distributed Optical Fiber Sensors

Real-time temperature mapping that solves local overheating problems is important for obtaining an optimized thermal design for high-efficiency power transformers. Internal temperature monitoring of operating power transformers can also be leveraged for asset monitoring applications targeting at fault detection enabling condition-based maintenance. Transformers present a variety of challenging sensing environments such as high levels of electromagnetic interference and limited space for conventional sensors to operate. Immersion of power transformers in insulation oils for thermal management during operation and the presence of relatively large and time-varying electrical and occasional magnetic fields make sensing technologies requiring electrical wires or active power at sensing locations highly undesirable. In this work, we investigate thermal response of a standard telecom fiber instrumented on compact transformer cores by using an optical frequency-domain reflectometry scheme. Correlation between conventional temperature sensing methods and fiber-optic sensing results as well as tradeoffs between spatial resolution and temperature measurement accuracy is discussed and spatially resolved real-time monitoring of temperatures in energized transformers is experimentally demonstrated.

Experimental evaluation of active power factor correction techniques in a single‐phase AC‐DC boost converter

SummaryThe increasing need to improve power quality with the reduction of the harmonic content of current and voltage waveforms has been intensively analyzed in several studies, thus motivating the proposal of many high power factor rectifiers based on the classic converters such as boost and buck‐boost. Moreover, distinct control techniques have also been proposed due to the commercial availability of integrated circuits (ICs) dedicated to impose sinusoidal input currents in switch‐mode power supplies (SMPSs). The boost converter operating in continuous conduction mode (CCM) is by far the most traditional choice for this purpose due to circuit simplicity and low electromagnetic interference (EMI) levels. Within this context, this work analyzes some of the most important control techniques used in power factor correction (PFC). The performance of a single‐phase boost converter using peak current mode control (PCMC), average current mode control (ACMC), and one cycle control (OCC) is evaluated experimentally in detail. A comprehensive analysis of key aspects such as the input current waveform and respective harmonic content, dc output voltage, and dynamic response of the converter is also presented.

Single‐switch, integrated DC–DC converter for high‐voltage step‐down applications

An integrated non-isolated DC-DC converter for applications that demand wide conversion range is proposed in this work. Using a technique known as graft scheme, it is possible to design a single-switch SEPIC-buck converter, where both the input current and the current supplied to the output stage composed of the filter capacitor and the load are non-pulsating when operation occurs in continuous conduction mode (CCM). Therefore, minimised electromagnetic interference (EMI) levels result as a consequence. Besides, the converter requires the use of a single active switch connected to the source reference node, without the need for isolated control circuitry, while it is possible to achieve wider conversion ranges than that provided by the classical buck converter. The qualitative and quantitative analysis of the converter is presented, from which it is possible to design and analyse it. Experimental results are discussed in detail to validate the theoretical considerations.

Vulnerability Assessment of a Multistate Component for IEMI Based on a Bayesian Method

A method based on the Bayesian approach is proposed in this paper to assess the vulnerability of a multistate component when the available experimental data are insufficient. According to the proposed definition of hierarchical vulnerability distributions, each state probability function of components is represented by adjacent level distributions, and the restriction of vulnerability distributions is analyzed. Depending on the credibility interval of the parameters of vulnerability distributions, the joint prior probability density functions (PDFs) of these parameters can be obtained in different scenarios. Therefore, the joint posterior PDF of these parameters can be obtained by combining the joint prior PDF and the likelihood function based on a Bayesian formula. Then, the posterior probability function of each state can be obtained by the proposed method. In realistic situations, the estimation of the state probability functions will be more practical than single estimation of the state probability under a specific threat level of intentional electromagnetic interference (IEMI). The specific process of the method is presented, while the hierarchical vulnerability distributions are represented by lognormal cumulative distribution functions. Finally, a case study demonstrates the effectiveness of the proposed method.

A Review of Spread-Spectrum-Based PWM Techniques—A Novel Fast Digital Implementation

Spread-spectrum (SS)-based pulsewidth modulation (PWM) techniques play an important role when tackling the electromagnetic interference (EMI) problem in the switch-mode power supply (SMPS) domain. They achieve the best EMI noise reduction and emerge as a promising and very effective solution to comply with electromagnetic standards. The current work provides an insight into the SS techniques: its history, its types, and mainly its ability to mitigate the EMI problem in the SMPS domain. Moreover, it gives a short review of the different SS-based PWM techniques going from the most basic and simple, i.e., the periodic modulation, to the most developed and complex, i.e., the random and chaotic modulations. Besides, a short review of the different implementation methods was addressed and they were categorized into analog and digital implementation techniques where its pros and cons were provided. Finally, a new fast digital implementation method based on a dsPIC33F microcontroller is presented. Its effectiveness was proved and its advantages over the reviewed implementation techniques were recognized. It reached a 20 dBuV EMI level reduction when the digital chaotic and periodic profiles were embedded into a boost converter prototype.

Nonlinear Dynamic Analysis of a Skyhook-Based Semi-Active Suspension System With Magneto-Rheological Damper

Response characteristics of a magneto-rheological suspension with a modified skyhook control scheme, focusing directly on the command current, were analyzed considering hysteresis nonlinearities. Suspension performance and its dynamic stability were investigated under harmonic excitation at frequencies up to 50 Hz to illustrate highly nonlinear influences of the excitation frequency and magnitude. The nonlinear response characteristics of the system, attributed to damper hysteresis and on–off control, were thoroughly analyzed considering the bifurcation diagrams, Lyapunov exponent spectra, phase portraits, and the Poincare maps. These, invariably, showed the presence of quasi-periodic, multiperiodic, and chaotic responses of the system under mid- as well as high-frequency excitations. The conducted electromagnetic interference (EMI) due to high frequency variations in the drive current, caused by the nonlinear system responses, was further evaluated using the method described in EN 55022 for the first time. The assessments using the GB9254 guidelines showed that the EMI levels exceed the recommended limits. The chaos-induced EMI may thus be detrimental to the electronic control systems of the automobile and cannot be ignored. This work is considered to serve as a theoretical foundation for future studies on EMI reduction and nonlinear control of intelligent semi-active suspensions.

Pseudo Random Pulse Driven Advanced In-Cell Touch Screen Panel for Spectrum Spread Electromagnetic Interference

For the first time, we analyze the mechanism of electromagnetic interference (EMI) in an advanced in-cell touch (AIT) panel, which is a state-of-the-art in-cell touch screen panel technology. The AIT panel has stronger EMI generation at a specific frequency band (0.15 ~ 30 MHz) due to a load free driving (LFD) method. The LFD is adopted to overcome the structural vulnerability of in-cell touch panel, which incurs large parasitic capacitance due to the touch electrodes within the display panel. In order to overcome the EMI problem, we present a novel driving method using pseudo random pulse (PRP). The power spectrum of PRP is well spread over the frequency band, resulting in a lower EMI. We measured the EMI level with a near-field probe, and the proposed driving method shows the EMI reduction of 6.5 dB. This EMI reduction is accomplished without structural reconfiguration, as well as the touch performance remains the same as that before PRP is applied. Therefore, the proposed driving method can be utilized in the field of automotive, military, and aviation industries as a user interface which requires high touch performance and low EMI generation due to the peculiarities.

Electrically Conductive Polymer Composite Dispensing Process for EMI Shielding Structure

Electro Magnetic Interference (EMI) shielding structure with low cost and high performance is proposed. Conductive polymer composite is formulated with metal based filler and silicone polymer and solvent. The liquid composite material can be easily dispensed through the low pressure injection nozzle and cured to the conformal structure with high aspect ratio. High electro conductive polymer composite dispensing process is developed to build a conformal structure for the EMI shielding of PBA(Printed Board Assembly). In order to increase electrical conductivity of composite material, Ag coated copper is adopted for conductive filler material and dendrite structure is applied to reduce content ratio of the conductive filler in the composite material. An EMI shielding structure is designed to cover the exposed surface of the chip package and modified for the shielding module containing chips and electrical elements on the PBA. The wall thickness of shielding layer is under 0.6mm and aspect ratio is lower than 2.0. The conformal structure is fabricated by dispensing process with side slot nozzle and viscoelastic behavior of composite material maintains the vertical thin wall structure. EMI shielding performance is verified by measurement of chip level EMI shielding test procedure developed in this study.

Internet of Vehicles for E-Health Applications: A Potential Game for Optimal Network Capacity

Wireless technologies are pervasive to support ubiquitous healthcare applications. However, a critical issue of using wireless communications under a healthcare scenario rests at the electromagnetic interference (EMI) caused by RF transmission, and a high level of EMI may lead to a critical malfunction of medical sensors. In view of EMI on medical sensors, we propose a power control algorithm under a noncooperative game theoretic framework to schedule data transmission. Our objective is to ensure that the noncooperative game of power control can achieve a network-level objective—the optimal network capacity, although the wireless users are selfish and only interested in optimizing their own channel capacity. To obtain this objective, we show that our proposed noncooperative game is a potential game and propose the best-response-dynamics algorithm which can ensure that the game strategy of each user is induced to the optimal solution to the problem of network-level optimal capacity. Numerical results illustrate that the proposed algorithm can achieve an enhancement of 8% of network performance than the existing algorithm against the variations of mobile hospital environments.

Design and application of a mobile miniature current probe for analysing the cause of EMI noise in IC circuits

This study is based on International Electrotechnical Commission (IEC) 61967-4 standards for measuring electromagnetic emissions and interferences at the chip level. Conventional measurement methods using fixed SMA connectors were replaced with an improved radio frequency current probe featuring semi-rigid coaxial cables, making it capable of taking mobile measurements, enhancing the flexibility and convenient probing usage. To effectively assess the practical value of the improved probe, the authors have referred to the standard designs provided in IEC 61967-1 to manufacture a four-layer digital circuit board that controls the screen of an on-board navigational screen for automobiles. Circuit board electromagnetic interference (EMI) noise frequency and level readings from the improved probe were also compared with three other measurement methods, namely magnetic field probes available in the market, TEM cells, and the 10-m far-field measurement method. The results demonstrated the capability of the improved probe to effectively identify sources of noise at the chip-level during the IC design phases, helping with root cause analysis and allowing EMI noises experienced by the product to be solved promptly during the process of electromagnetic compatibility design optimisation and analysis.

Family of soft‐switching pulse‐width modulation converters using coupled passive snubber

Efficiency, power density and electromagnetic interference (EMI) stand among the main concerns in power electronics and determine the quality of a power converter. To address the aforementioned concerns, this study proposes a cost effective passive soft-switching technique using coupled inductor for pulse-width modulation (PWM) converters. Through providing soft-switching conditions, switching losses are reduced and the use of coupled inductor technique improves the power density. Since, the slope of voltage and current variations over time is reduced by the proposed passive soft-switching technique, the EMI level is expected to reduce. This technique can be applied to a wide range of PWM converters, however, the analysis is focused on a soft-switching boost converter to provide a framework. The experimental measurements of the realised 200 W boost converter show that the efficiency is improved by 2 and 3.8% as compared to a hard switching boost converter with and without an RCD snubber circuit, respectively. Moreover, the experimental EMI measurements indicate that with no external EMI filter, the proposed technique has reduced the main peak of EMI level by 8 dBµV (in comparison to its hard switching counterpart) which satisfies CISPR22 class A EMC standard limitation.

Differential Mode Conducted EMI Prediction in Three Phase SiC Inverters

With the application of Silicon carbide (SiC) power MOSFETs in three phase inverters, higher level electromagnetic interference (EMI) produced. Thus, it is more urgent to predict EMI level in the design phase. This paper describes a frequency-domain approach to predict differential mode(DM) EMI of three phase SiC inverters. Both noise path and DM noise source are modeled. The calculated result is compared with experimental result and they agree well with each other. It is indicated that the proposed method with accurate noise and path modeling is an effective method for DM prediction of the system.

Interference and Electromagnetic Compatibility Challenges in 5G Wireless Network Deployments

<p>5G wireless network technology is going operate within the environment of other electrical, electronic and electromagnetic devices, components and systems, with capability of high speed data connectivity acting as network transceiver stations with Massive MIMO for Internet of Things (IoT). Considering the level of interoperability, electromagnetic Interference and electromagnetic compatibility to avoid electromagnetic pulse effects (EMP) which is capable of not only causing network malfunctions but total devices and equipments failure in mission critical operations, like hospital MRI scan machines, security profiling and data handling or even personal healthcare devices like heart pacemaker. Electromagnetic energy coupling in PCB due to: radiation, reflection and Crosstalk generates reliability challenges affecting Signal Integrity between traces of multilayer boards stalks, power bus and packaging creating Electromagnetic interference (EMI) in PCB leading false clock response to system failure. Above were considered very essential when deploying 5G wireless network facility as presented in this paper. </p>

Hybrid Visible Light and Ultrasound-Based Sensor for Distance Estimation.

Distance estimation plays an important role in location-based services, which has become very popular in recent years. In this paper, a new short range cricket sensor-based approach is proposed for indoor location applications. This solution uses Time Difference of Arrival (TDoA) between an optical and an ultrasound signal which are transmitted simultaneously, to estimate the distance from the base station to the mobile receiver. The measurement of the TDoA at the mobile receiver endpoint is proportional to the distance. The use of optical and ultrasound signals instead of the conventional radio wave signal makes the proposed approach suitable for environments with high levels of electromagnetic interference or where the propagation of radio frequencies is entirely restricted. Furthermore, unlike classical cricket systems, a double-way measurement procedure is introduced, allowing both the base station and mobile node to perform distance estimation simultaneously.

User-Priority-Based Power Control Over the D2D Assisted Internet of Vehicles for Mobile Health

A device-to-device (D2D) assisted cellular network is pervasive to support ubiquitous healthcare applications, since it is expected to bring the significant benefits of improving user throughput, extending the battery life of mobiles, etc. However, D2D and cellular communications in the same network may cause cross-tier interference (CTI) to each other. Also a critical issue of using D2D assisted cellular networks under a healthcare scenario is the electromagnetic interference (EMI) caused by RF transmission, and a high level of EMI may lead to a critical malfunction of medical equipments. In consideration of CTI and EMI, we study the problem of optimizing individual channel rates of the mobile users in different priorities (different levels of emergency) within the Internet of Vehicles for mobile health, and propose an algorithm of controlling the transmit power to solve the above-mentioned problem under a game-theoretical framework. Numerical results show that the proposed algorithm can converge linearly to the optimum, while ensuring an allowable level of EMI on medical equipments.

User-Priority-Based Power Control in D2D Networks for Mobile Health

A device-to-device (D2D) assisted cellular network is pervasive to support ubiquitous healthcare applications, since it is expected to bring the significant benefits of improving user throughput, extending the battery life of mobiles, etc. However, D2D and cellular communications in the same network may cause cross-tier interference (CTI) to each other. Also a critical issue of using D2D assisted cellular networks under a healthcare scenario is the electromagnetic interference (EMI) caused by RF transmission, and a high level of EMI may lead to a critical malfunction of medical equipments. In consideration of CTI and EMI, we study the problem of optimizing the energy efficiency (EE) across the mobile users in different priorities (different levels of emergency) within the Internet of vehicles for mobile health, and propose a penalty-function algorithm of power control to solve the aforementioned problem. Numerical results demonstrate that the proposed algorithm can achieve remarkable improvements in terms of EE, while ensuring an allowable level of EMI on medical equipments.

Оценка электромагнитной помехи в электросети ракеты при прямом попадании в нее молнии

Оценка электромагнитной помехи в электросети ракеты при прямом попадании в нее молнии

Measurement of transient electromagnetic coupling and interference caused by disconnector operation in substation

Abstract Disconnector operation in the substation can cause transient electromagnetic disturbance and very fast transient over-voltage (VFTO), and will lead to the misoperation or damage of electrical protection system. To research the characteristics and influence of electromagnetic interference, principle of disconnector operation was analyzed. Then, an improved Agrawal model was adopted to describe the transmission line coupling process of disconnector operation, and telegraph equation was calculated by finite-difference time-domain (FDTD) method. With the model and method, the conduction process and characteristics of transient electromagnetic coupling and interference caused by disconnector operation in substation were simulated. Besides, disturbance voltage signal on the secondary cables caused by disconnector operation was measured in a 500 kV substation. Finally, parameters of transient electromagnetic coupling and interference in time domain and frequency domain were calculated respectively. Experiment results show that the quantitative level of transient electromagnetic coupling and interference caused by disconnector operation in substation can be evaluated in theory, and the core frequency points concerned in secondary circuit can be calculated.

Simultaneous realization of electromagnetic interference shielding, hydrophobic qualities, and strong antibacterial activity for transparent electronic devices

Al (3 at%)-doped ZnO (AZO)/Ag/AZO multilayer films annealed at 100 °C for 20 min under an oxygen atmosphere were examined for electromagnetic interference (EMI) shielding, hydrophobic qualities, and antibacterial activity for use in transparent glass panels. The annealed AZO (45 nm)/Ag (9 nm)/AZO (45 nm)/glass multilayer films showed a high level of EMI shielding effectiveness in the Bluetooth frequency range (∼39 dB) and strong antibacterial activity against Escherichia coli and Staphylococcus aureus. The annealed multilayer films demonstrated high levels of transmittance (∼90%) and conferred hydrophobic qualities to previously hydrophilic as-deposited films.

Electromagnetic interference in electrical systems of motor vehicles

Electronic ignition system affects the electronic equipment of the vehicle by electric and magnetic fields. The measurement of radio electromagnetic interference originating from the ignition system affecting the audiovisual test bench was carried out with a variable speed of the ignition system. The paper presents measurements of radio electromagnetic interference in automobiles. In order to determine the level of electromagnetic interference, the audiovisual test bench was equipped with a set of meters for power consumption and assessment of the level of electromagnetic interference. Measurements of the electromagnetic interference level within the audiovisual system were performed on an experimental test bench consisting of the ignition system, starting system and charging system with an alternator and regulator.