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Three-phase induction motors are widely used in industrial facilities, where the maintenance of these machines is preponderant for industrial processes. Recent research reports that vibration-based data acquisition is the most common approach to perform bearing condition monitoring because it can extract more relevant information. However, the acquisition of vibration-based signals is expensive, requiring accelerometers and other external devices to transmit and process the signal information. Otherwise, current-based signals are directly measured by the supply system or inverters, enabling the current-based data acquisition in most industrial cases. In this context, this work introduces a new current-based method to identify bearing damages, applying artificial intelligence algorithms. Experimental and on-site tests present promising results, validating this approach for bearing damage diagnosis.

Direct model predictive control (DMPC) of permanent magnet synchronous generators with full-scale back-to-back (BTB) converters plays an important role in improving the power quality injected to the grid and to comply with grid codes. However, DMPC suffers from the excessive computational burden since all the feasible voltage vectors (VVs) of the BTB converter are used for the prediction and evaluation. Moreover, the weighting factor in the cost function may affect the control performance and tuning it is a complex process. Accordingly, benefiting from the simplicity of the direct control techniques, new direct model predictive flux and power control are proposed in this article, in combination with the direct torque and power control (DTC and DPC), respectively. By defining new DTC and DPC switching tables, only three out of the eight predictions are required to select the best VV for each converter of the BTB topology, which significantly reduces the algorithm computations. To avoid the weighting factor, the electromagnetic torque is simply converted into an equivalent stator flux and only the latter one is considered in the cost function. Experimental results prove that the execution time can be reduced by 26.9%, while the best control performance can be achieved.

The adoption of light-emitting diodes (LEDs) for lighting applications is becoming increasingly relevant as this recent technology is advancing. Given the recent uptake of LED lighting technologies for distinctive end-uses, the research community has also committed to the development of an ever-increasing range of power electronic converters that are suitable for yielding maximum quality lighting, high efficiency, and long lifetimes. As one of the most recent and promising technologies of the moment, it is vital to fully understand the performance and merits of each state-of-the-art LED lighting technology. Accordingly, this paper compiles essential information about a broad range of state-of-the-art LED lighting systems, aiming to compare their performances in terms of efficiency. Based on the comparative analysis, the main merits and drawbacks of each LED lighting system architecture are obtained. Then, a detailed evaluation of the performance of a particular LED lighting system and the corresponding control strategy is developed, thereby enabling a clear view of the evolution of the performance of the system as a function of parameters like supply voltage and number of driver channels.

Faults in aluminum electrolytic capacitors (AECs) are classified as the major cause for power electronics equipment breakdown, mainly due to AECs wear out through the vaporization of the electrolyte, as a result of both aging and temperature effects. The majority of manufacturers identify the end-of-life threshold of such capacitors as their equivalent series resistance (ESR) increases by 80% or their capacitance (C) decreases by 20%, relative to their initial values. Therefore, the online estimation of these two parameters can provide valuable and timely information that allows detecting any potential capacitor failure. Changes in C and ESR parameters influence the relationship between the capacitor voltage and current ripples. This ratio is dominated by C at low frequencies, and by ESR in the high-frequency range. The aim of this article is to propose an algorithm allowing a continuous estimation and tracking of both parameters (ESR and C). This algorithm should be simple, fast, and suitable for online implementation. Therefore, this article introduces the use of the short-time Fourier transform (STFT) technique to determine and track C and ESR values, starting from some always-existing harmonics at low and high frequencies. The STFT is based on applying the discrete Fourier transform algorithm on a sliding window, which makes it more appropriate for online implementation. The effectiveness of the proposed method is proved by simulation and laboratory experiments, using a boost dc–dc converter.

In this article, the occurrence of stator faults in line-start permanent magnet synchronous motors is analyzed. A dynamic model of the motor was developed in MATLAB/Simulink, which considers the performance of the motor both in healthy conditions and under the occurrence of interturn short-circuit faults, at an early stage of development. To validate the presented approach, simulation results, covering the full range of operation, and different fault severity levels, are compared with the motor experimental performance. The output of the proposed model, namely voltages and currents, present a good agreement with experimental results, demonstrating the accuracy of the proposed model. Additionally, an online fault diagnostic technique is explored, demonstrating its potentiality.

This paper proposes a single inductor multiple output (SIMO) driver architecture for RGB LEDs with hybrid dimming technique, for use in large installation, with minimal loss of luminous flux and light flickering. Among other benefits, the proposed dimming technique provides improved accuracy in the color control, while maintaining low current ripple. Such advantages are easily attained, even when resorting to a simple SIMO LED driver. To confirm the effectiveness of the proposed hardware and software architecture, a comprehensive set of scenarios is established and tested resorting to a simulation model of the LED system.

Background and Study Aims Single-level circumferential or pincer stenosis (PS) affects few patients with degenerative cervical myelopathy (DCM). The surgical technique and medium-term results of a one-session microsurgical 360-degree (m360°) procedure are presented. Patients Between 2013 and 2018, the data of 23 patients were prospectively collected out of 371 patients with DCM. The m360° procedure comprised a microsurgical anterior cervical decompression and fusion (ACDF), with additional plate fixation, followed by flipping the patient and performing a microsurgical posterior bilateral decompression via a unilateral approach in crossover technique. Results The mean age of the patients was 72 years (range: 50–84); 17 patients were males. The mean follow-up time was 12 months (range: 6–31). The patients filled in the patient-derived modified Japanese Orthopaedic Association (P-mJOA) questionnaire on average 53 months after surgery. One patient received a two-level ACDF. Lesions were mostly (92%) located at the C3/C4 (8/24), C4/C5 (7/24), and C5/C6 (7/24) levels. Functional X-rays showed segmental instability in 10 of 23 patients (44%). All preoperative T2-weighted magnetic resonance imaging (MRI) showed an intramedullary hyperintensity. The median preoperative mJOA score was 13 (range 3), and it improved to 16 (range 3) postoperatively. The mean improvement rate in the mJOA score was 73%. When available, postoperative MRI confirmed good circumferential decompression with persistent intramedullary hyperintensity. There were two complications: a long-lasting radicular paresthesia at C6 and a transient C5 palsy. No revision surgery was required. Conclusion The one-session m360° procedure was found to be a safe surgical procedure for the treatment of PS, and the medium-term clinical outcome was satisfactory.

Research on fault detection (FD) and condition monitoring (CM) of rotating electrical generators for modern wind turbines has addressed a wide variety of technologies. Among these, permanent magnet synchronous generators (PMSGs) and the analysis of their electromagnetic signatures in the presence of faults deserve emphasis in this paper. PMSGs are prominent in the offshore wind industry, and methods for FD and CM of PMSGs based on electromagnetic measurements are extensively discussed in academia. This paper is a concise review of FD and CM in wind turbines and PMSGs. Terminology and fundamentals of PMSG’s operation are introduced first, aiming to offer an easy read and good reference to a broad audience of engineers and data scientists. Experience and research challenges with stator winding failures are also discussed.

Objectives: Home dwelling people with dementia and their informal carers often do not receive the formal care services they need. This study examined and mapped the research regarding interventions to improve access and use of formal community care services. Method: This is a scoping review with searches in PubMed, CINAHL, PsychINFO, Medline, Cochrane Database of Systematic Reviews, Social Science Citation index and searches of grey literature in international and national databases. Studies were categorized according to the measure used to enhance access or use. Results: From international databases, 2833 studies were retrieved, 11 were included. Five studies were included from other sources. In total, 16 studies published between 1989 and 2018 were examined; seven randomized controlled trials, six pretest-posttest studies and three non-randomized controlled studies. Sample sizes varied from 29 to 2682 participants, follow-up from four weeks to four years. Five types of interventions were identified: Case management, monetary support, referral enhancing, awareness & information focused and inpatient focused. Only two studies had access or use of community services as the primary outcome. Fourteen studies, representing all five types of interventions, had positive effects on one or more relevant outcomes. Two interventions had no effect on relevant outcomes. Conclusion: The included studies varied widely regarding design, type of intervention and outcomes. Based on this, the evidence base for interventions to enhance access to and use of formal community services is judged to be limited. The most studied type of intervention was case management. More research is recommended in this field.

Condition monitoring is an essential technology for detecting various incipient defects in electrical machines. Stator inter-turn and rotor broken bar faults are two major faults of the squirrel cage induction motors (SCIMs). Many attempts have been made to provide fault diagnosis systems for detecting the faults individually. This study proposes a novel unified fault diagnosis system for detecting the faults and identifying their exact severities. The system is based on a flexible model of the SCIM and can identify the severities of the faults even if they are presenting simultaneously. Robustness against the motor load change, the unbalance degree of the voltage supply and its distortion are the other merits of the proposed fault diagnosis system. Experimental results under various fault modes and operating conditions demonstrate the effectiveness of the proposed fault identification technique.

Cement is considered the basic component with the highest environmental impact in construction, in terms of CO2 emissions. As for the aggregates, the process of comminution of rocks, in addition to artificial sand, generates stone powder that ends up being stored outdoors, generating environmental damages. Thus, the replacement of cement by stone powder appears as an attractive alternative towards the sustainable concretes. In this context, the objective of this paper is to determine the maximum packing density in Portland cement, silica fume and stone dust pastes, to determine the optimal cement substitution content for the stone powder. In addition, it is intended to verify the influence of excess water on the consistency of the mixtures produced. The substitution was done in contents equal to 0%, 7%, 14% and 21% by volume and, for each content, the packing density was determined analytically by CPM model and combinations were reproduced experimentally. Excess water was checked by the mini Kantro cone test. The results showed that the higher cement substitution content of the stone powder obtained the higher packing density, experimental and analytical, and the higher workability, allowing economic and environmental advantages. Analyzing each material, the stone powder resulted in the highest packing density and silica fume is the lowest one. Therefore, finer particles resulted in lower packaging densities, due to the greater specific surface area, which demands more water. The agglomeration resulted in more empty gaps between the grains. In addition, mixtures flowability increased with the increase of the stone powder content. As the excess water is responsible for mixture lubrication, a higher packing density for a given volume of water improves the flowability. Resumo O cimento Portland é considerado o componente de base com o maior impacto ambiental na construção civil, em termos de emissões de CO2. Quanto aos agregados, o processo de cominuição das rochas, além da areia artificial, gera pó de pedra que acaba sendo armazenado ao ar livre, gerando impactos ambientais. Assim, a substituição do cimento por pó de pedra aparece como uma alternativa atraente em direção à dosagem de concretos sustentáveis. Nesse contexto, o objetivo do presente trabalho é determinar a máxima densidade de empacotamento de partículas em pastas compostas por cimento Portland, sílica ativa e pó de pedra, buscando determinar o teor ótimo de substituição do cimento pelo pó de pedra. Além disso, pretende-se verificar a influência do excesso de água na consistência das pastas produzidas. A substituição do cimento por pó de pedra foi feita em teores iguais a 0%, 7%, 14% e 21%, em volume, sendo determinada a densidade de empacotamento analiticamente, pelo modelo CPM. As combinações foram reproduzidas experimentalmente. A consistência das pastas foi verificada com auxílio do mini cone de Kantro. Os resultados demonstraram que o maior teor de substituição do cimento pelo pó de pedra apresentou a maior densidade de empacotamento, experimental e analítica, e a maior trabalhabilidade, permitindo vantagens econômicas e ambientais. Analisando cada material individualmente, o pó de pedra apresentou a maior densidade de empacotamento e a sílica ativa a menor. Partículas finas resultam em menor densidade de empacotamento, devido à maior superfície específica, a qual demanda mais água. A aglomeração aumenta os vazios entre os grãos. Além disso, a fluidez das pastas produzidas aumentou com o acréscimo do teor de pó de pedra. Como o excesso de água é o responsável pela lubrificação da pasta, uma densidade de empacotamento mais elevada colabora para o aumento da fluidez quando o volume de água permanece fixo.

Insulation monitoring systems in electrical networks and industrial loads are necessary for the reliable operation of equipment, and to reduce the risk of accidents and short-circuits in the load. In all energized electrical networks, the insulation resistance of the circuits is continuously monitored, which is the main indicator of the health of electrical equipment. In case of damage of the sheath of cable lines or insulation of electrical equipment (transformers, power buses, windings of electrical machines, etc.), monitoring systems allow to timely detect and eliminate equipment malfunctions. The use of a constant voltage connected to the monitored network makes it possible to control the insulation of the entire electrical network. Maintenance personnel in the future have to take measures to localize the malfunction and find the exact location of the insulation damage. Such searches can be difficult and time-consuming in distributed electrical networks with a large amount of loads. To speed up the search, insulation monitoring systems of a galvanically coupled load with leakage current sensors are used to determine which load in the network caused a decrease in the overall insulation. For this, the property of symmetry of three-phase electrical circuits is used, for which the sum of the three-phase currents is zero, provided that the currents in the phases are symmetrical. Thus, the magnetic circuit of the leakage current sensor is magnetized only by the direct current from the test voltage source. The value of this leakage current will be proportional to the insulation on the load side. In the presence of a large number of consumers, such a monitoring system allows to determine the location of the damage without disconnecting the power supply from the load. In insulation monitoring systems for autonomous objects, for example, large ships, this allows to reduce the time for troubleshooting - without stopping the operation of all mechanisms, which is especially important on ships with a nuclear installation (icebreakers), where it is unacceptable to disconnect especially important electric drives that ensure the operation of the reactor. The measurement accuracy of the leakage current sensors is determined, among other things, by the symmetry of the three-phase load currents, and in the presence of distortions and nonlinear phenomena, the measurement error appears, the greater - the greater the distortion. This article is devoted to the assessment of the contribution of distortions to the measurement accuracy of such insulation monitoring systems.

This paper presents an approach that can be very useful for the design, analysis, and simulation of AC-DC converters. The equations used for design purposes should allow the calculation of the parameters of the components that make up these converters with a high safety margin, since these components are normally subjected to a high level of electrical stress. On the other hand, as these components have a shorter life span, when compared to the rest of the system, their parameters, in the design context, must be oversized. However, regarding the analysis, the equations that allow the description of their main characteristics must be much more precise. Therefore, the equations used in the project should not be used for analysis purposes. Thus, some recommendations will be presented regarding the use of both equations. On the other hand, the choice of oversized elements can lead to other problems, particularly in the case of capacitors. This issue will be discussed in this paper, and some solutions to this problem will be presented. The recommendations and conclusions presented in this paper were obtained by taking into account several simulation results performed in Python programming language and for that purpose, it was necessary to create several Python scripts.

Aluminum electrolytic capacitors (AECs) are widely used in the DC link of power converters, such as the DC-DC interleaved boost converter (IBC), which offers many advantages over the conventional amplifier converter. It is well known that AECs failures represent the major cause for breakdown of power electronics equipment. Hence, the development of robust control strategies, that allow to evaluate the electrolytic capacitor state, while keeping the performance of the converter control strategies, even under the occurrence of a capacitor fault, gains further emphasis. For that purpose, model-based predictive control (MBPC) applied to power electronics is a hot research topic that has been receiving the attention of researchers, given its advantages in terms of robustness, reduced tuning effort and, when applicable, fault tolerance. In turn, model-free predictive control (MFPC) is an underdeveloped research topic, that requires further efforts. To the best of the authors' knowledge, the literature does not report any MFPC strategy aimed at DC-DC converters. Accordingly, this paper proposes the combination of a novel MFPC strategy with the Short Time Fourier Transform (STFT) method, aiming to perform an online estimation of the ESR and C parameters, thus allowing a continuous evaluation of the electrolytic capacitor condition and, consequently, avoid a total system failure. The effectiveness of the proposed strategy is verified by several experimental tests.

LED lighting systems based on multi-output centralised control units are gaining increased popularity, in both indoor and outdoor environments, thanks to their benefits in terms of cost-effectiveness and ease of maintenance. Unfortunately, this approach also brings in some technical challenges. One of the critical constraints to account for in large-scale LED lighting systems with centralised control units is the parasitic inductances and resistances introduced by long cabling, which limits the luminous flux of LED lights well below the desired level. This paper presents an improved current compensation control strategy, for single-inductor multiple-output (SIMO) LED drivers, which features three major advantages in comparison to the state-of-the-art solutions: 1) the requirement of current compensating hardware is fully eliminated, thus reducing the total cost of the lighting system; 2) the current compensation strategy can be also adopted for the fault-tolerant operation of LED drivers; and 3) none of the LED fixtures suffer depreciation of luminous flux. Simulation and experimental results demonstrate the effectiveness of the proposed software-based current compensation strategy.

This paper addresses the occurrence of stator faults in six-phase induction machines, with a symmetrical winding. A dynamic model of the motor was developed in Matlab/Simulink environment, taking into consideration the occurrence of inter-turn short circuit faults. To validate the proposed approach, simulation results, covering the full range of operation and different fault severity levels, are compared with the motor experimental performance. The obtained voltages and currents present a good agreement with the corresponding experimental results, demonstrating the accuracy of the proposed model.

Wind turbines are nowadays very important for a significant contribution to the supply of electricity. Since the composition of such electrical networks includes generators of relatively low power, this leads to the need for parallel operation of several generators to satisfy large energy demands. To do this, it is necessary to control the voltage and frequency parameters at the output of generators, that is impossible in conventional synchronous generators with permanent magnets. The problem posed can be solved by using a doubly-fed machine as electric generator, which makes it possible to control the voltage and frequency parameters at the output of the electric generator, regardless of the rotation speed of the wind turbine shaft. In contrast to the currently used double conversion of electricity (rectification, inversion), in this case, it is not necessary to carry out the conversion of energy to the full power of the wind turbine. It is possible to reduce the power of the inverter and thereby increase the efficiency and reliability of the entire wind turbine. The load is connected to the stator winding of the generator, which gives a high quality of electricity supplied to the electrical network. The article also discusses the dynamic modes of a wind turbine with an electric generator based on a doubly-fed machine. The frequency dependencies for both leading and lagging modes of the shaft rotation speed, as a function of the nominal value, have also been obtained.

This paper evaluates the feasibility of wide-bandgap semiconductors as a replacement for silicon semiconductors, applied in a full bridge resonant converter for EV and HEV magnetically coupled resonant wireless power transfer, as a way to increase the efficiency of the process. The work consists of a series of simulations to study the impact of different input voltages, switching frequencies, and output load values on the overall efficiency of the system, for three distinct semiconductor technologies: Si MOSFET, GaN transistor, and SiC MOSFET.

Artificial intelligence algorithms and vibration signature monitoring are recurrent approaches to perform early bearing damage identification in induction motors. This approach is unfeasible in most industrial applications because these machines are unable to perform their nominal functions under damaged conditions. In addition, many machines are installed at inaccessible sites or their housing prevents the setting of new sensors. Otherwise, current signature monitoring is available in most industrial machines because the devices that control, supply and protect these systems use the stator current. Another significant advantage is that the stator phases lose symmetry in bearing damaged conditions and, therefore, are multiple independent sources. Thus, this paper introduces a new approach based on fractional wavelet denoising and a deep learning algorithm to perform a bearing damage diagnosis from stator currents. Several convolutional neural networks extract features from multiple sources to perform supervised learning. An information fusion (IF) algorithm then creates a new feature set and performs the classification. Furthermore, this paper introduces a new method to achieve positive unlabeled learning. The flattened layer of several feature maps inputs the fuzzy c-means algorithm to perform a novelty detection instead of clusterization in a dynamic IF context. Experimental and on-site tests are reported with promising results.

This paper presents a technique that can be used in the design of step-up regulated linear power supplies. The proposed technique enables the proper selection of the components that compose the power supply. This power supply increases its input voltage through a full wave voltage doubler, which replaces the typical full bridge rectifier. The selection of the capacitors that compound the voltage doubler is not simple, particularly, when a current-hungry load is connected to the circuit. In this paper a detailed analysis of a full wave voltage doubler is carried out, and simultaneously some design formulas are presented, that can be used very prolifically during the design process. To demonstrate the applicability of the proposed technique an experimental prototype was assembled.

The advancement of drug delivery devices is critical for the individualization of patient treatment and the improvement of healthcare. Here, we introduce the 3DMNMEMS, a novel device that combines 3D printing, microneedles (MNs) and Microelectromechanical Systems (MEMS), allowing versatile and controllable by the user transdermal drug delivery. Hollow MNs were designed and 3D printed using Stereolithography, followed by integrating into a MEMS. By employing advanced imaging techniques, we monitored the distribution of liquid delivered by the device within skin tissue in real-time. In vivo testing revealed that the delivery of insulin using the 3DMNMEMS achieved improved glycemic control to diabetic animals compared to subcutaneous injections. These results demonstrated the potential of the 3DMNMEMS as a universal transdermal drug delivery system for personalized care.

A system for semi-automated plant phenotyping is being developed in Portugal within the framework of the INTERPHENO project from the EU Programme "Portugal 2020." As a part of this activity, we tested two induced fluorescence techniques based on the laser and flashlamp excitation to facilitate the recognition of plants and photosynthetic state assessment based on the emission spectra.

Silica fume (SF) is the most commonly mineral admixture used for the production of high-strength concrete (HSC) due to its chemical characteristics of pozzolanic reactivity and physical filling effect. The objective of the present work is to compare the SF content by the chemical analysis of the pozzolanic reaction and the physical behavior by particle packing techniques. The first step of the study was to analyze the SF content to consume the calcium hydroxide (CH) produced during the hydration of Portland cement (PC), based on stoichiometric calculations. Then, the SF content for maximum packing density was obtained using analytical particle packing models and experimental tests. The compressive strength of the pastes was also measured. The results showed that the theoretical SF content for consuming CH is 15.6%, replacing PC. According to the packing density analytical models, the ideal SF content is 15% of the total fine materials. However, the experimental results indicated the use of a smaller SF content (10%). This difference between theoretical and experimental results is probably due to the high specific surface of the SF, which results in important surface forces between the grains, particle agglomeration and difficulty in SF densification with water.

Large sea ships take a huge part in world trade, passenger transport and providing supply to remote areas. There are various ship classes, designed not only for transportation of goods, but also to perform special tasks. The mentioned type of ships includes icebreakers designed to support navigation in the Arctic region. They are distinguished by a large displacement and high-capacity propulsion plant, as well as a dynamic mode of operation with frequent reverses. Many other ship types also use an electric drive in their propulsion systems, which is due to operating conditions and reliability requirements. Electric propulsion systems have the ability to change the direction of rotation with frequent repeated cycles. Currently, AC electric propulsion systems are used most widely, replacing obsolete DC motors. With a retrospective view of electric propulsion systems, a sequential development becomes obvious. The modern marine electric drive should be further improved in terms of its capacity and operation cost-effectiveness. The last of these tasks is mainly to increase efficiency and reduce losses both when converting the frequency of the supply voltage and in general in all parts of the electric propulsion system. In practice, with the modern development of technology, the reserve for improving properties of electric components is not so great. In this case, the single way to increase the efficiency of shipboard electric propulsion systems is reducing the number of functional units on the way from ship generators to the engine motor. The authors proposed a number of technical solutions for improving ship electrical propulsion systems; the novelty is confirmed by patents for inventions. One of the solution effects is the simplification of the functional circuit of the electric propulsion system, which corresponds to the general development trend- a decrease in the number of functional units and elements on the way from the ship energy source to the electric engine.

Electric drives are used in industrial installations for the mechanical movement of various kinds of goods, in pumps, as well as in transport installations to bring them into motion. An electric drive includes an actuator (motor) and a frequency converter, as well as a control system that provides soft start, reverse and speed control. The most complex part of the electric drive is the frequency converter, so the probability of the occurrence of a failure of the entire system depends on its reliability. Currently, inverters are used, based on a three-phase bridge with IGBT transistors; its circuitry has made it possible to minimize the number of elements, which was especially relevant earlier when using thyristors with forced switching. Currently, they are replaced by fully controllable insulated gate transistors, which reduced the number of elements in power circuits, and also simplified control algorithms - thereby increasing the reliability of electric drives in general. However, a further improvement in the characteristics of the electric drive is still associated with the improvement of the frequency converter. In this paper it is proposed to replace the three-phase bridge circuit in the inverter with three single-phase channels according to the full-bridge circuit in each of them; the phase outputs are connected in series according to the star circuit. The main difference between this option is the presence of a common neutral at the inverter output, the tap from which is not present in three-phase bridge circuits. In this case, in the event of an accident in one of the phases, it is possible to connect the corresponding phase of the motor to the inverter neutral, which, when correcting the shift angle between the remaining two phases of the inverter by an angle of 60°, ensures the formation of a symmetric three-phase voltage system on the motor stator. This made it possible to abandon the reservation of a three-phase bridge circuit, requiring two sets of 3 phases each on the motor stator, provided that their neutrals were isolated, and such systems are essentially six-phase. The electric drive described in this article has redundancy that is not inferior to the currently used systems and has several advantages - these include maintaining 2/3 of the rated power during emergency phase shutdown, and the operation of the electric motor in symmetric mode; also the advantages include the possibility of forming a three-level voltage without capacitors in the DC link. In general, the proposed solution has a low cost while maintaining reliability, as well as the quality of voltage and currents in nominal mode.

International audience; This paper introduces a simple and low-cost direct vector control method without current sensors for Permanent Magnet Synchronous Motor (PMSM) drives, using only a single estimator and the measured dc-link voltage, as well as the measured rotor speed for currents reconstruction. The proposed method is based on a new modification of the adaptive state observer to estimate the line currents. A theoretical concept is developed, the modified adaptive state observer is presented. Simulations tests are performed to prove the ability of the proposed scheme to reconstruct stator currents and reproduce the performances of a basic and traditional vector control PMSM drive.

The design of a brushless generator, with excitation from permanent magnets, is proposed in this paper. A distinctive feature is the passage of magnetic flux in the direction longitudinal to the axis of rotation of the rotor, which made it possible to change the design of the generator. A permanent magnet is used for the excitation. It is placed in the center of the rotor of the generator, and magnetized in the longitudinal direction. At the ends of the rotor, the poles made of the ferromagnetic material are installed, which serve to distribute the magnetic flux excitation along the teeth of the stator, and the stator itself can be made of plastic or other non-magnetic materials, such as ceramics. This is due to the change in the direction of the passage of the magnetic flux excitation from transverse to longitudinal, so the main frame of the stator can be made of non-magnetic material. The magnetic core is an array of rectangular pins located around the circumference, inside the stator, in the longitudinal direction. The coils of the output winding are installed in the middle of the pins, and cutouts in the area of the pins installation are provided in the non-magnetic stator. Thus, during the assembly of the generator stator, the pins of the charged ferromagnetic material are installed in the assembly with the output winding coils, and the corresponding cutouts from the inside of the stator are used for fastening. Cutouts improve heat dissipation from coils as they come in contact with the external environment. The listed design features of the generator provide a cost reduction, which is especially important for the small and medium power range applications. It is established that the proposed generator design is characterized by a double frequency of the output voltage.

Aluminum electrolytic capacitors (AECs) are the most common capacitors used in power electronics. They are frequently used for filtering and storage functions because of their small size, large capacitance, and low price. However, AECs also represent the major cause for power electronics equipment breakdown, mainly due to their wear out through the vaporization of the electrolyte, as a result of both aging and temperature effects. The aging of AECs is expressed by the increase of their equivalent series resistance (ESR) and the decrease of their capacitance ( C ). Therefore, estimating these two parameters can provide a good indicator for a potential capacitor failure. Additionally, these changes in C and ESR parameters strongly influence the ratio between the capacitors voltage ripple and their current ripple. This ratio is dominated by C at low frequencies and by the ESR in the high-frequency range. Hence, this paper suggests a method for online estimating and tracking of both C and ESR using that ratio, which is computed starting from some always existing harmonics at low and high frequencies. The proposed method uses the short time least square Prony's (STLSP) technique to determine and track the amplitudes of the target harmonics. It is shown that compared with the discrete Fourier transform method, the STLSP technique is well suitable for such application, since it has the ability to determine and track the amplitude and frequency of any spectral component, even for noisy and nonstationary signals, using a small number of data samples. This reduces a lot the data storage requirements. Consequently, the proposed method is appropriate for online implementation. The method's effectiveness is proved by simulation and experimental tests using a boost dc–dc converter.

Motor current signature analysis (MCSA) based detection of rotor cage faults (RFs) in medium-high voltage induction motors has become common in the field due to its low-cost remote monitoring capability. However, low-frequency load oscillations (LOs) in applications that employ speed reduction couplings can induce frequency components in the vicinity of that of RFs. It has been reported that false-positive or -negative RF indications can be produced with the MCSA, if the frequency components produced by RF and LO overlap. There, recently, have been studies on discriminating RF and LO; however, the case where two harmonic components overlap at the same frequency, which is the most difficult and serious case, has not been investigated. In this paper, a spectrum analysis of instantaneous active and reactive power is applied, and it is shown that RF and LO can be separated for the case where the MCSA fails due to the overlap in the two spectral components. An experimental study performed on a 380 V motor with a speed reduction gear shows that RF and LO can be reliably detected and separated for avoiding false RF indications.

The interturn faults are one of the most (if not the most) challenging electrical machine failures to detect online and at incipient severity stages. Past works and experience have shown that this specific fault type will lead to a ground fault and consequently a catastrophic failure of the machine in a very small amount of time. Past works have proposed techniques and methodologies to confront this dangerous fault. However, a common feature in most past efforts is the high level of severity, limited by external resistors to avoid machine breakdowns. Scenarios like the above are not of much use in industry because they lead to the development of diagnostic techniques insensitive to the real fault severity levels that are noncatastrophic and that are by their nature very low. This is the motivation behind this article, which challenges the existing background in this field and offers a reliable solution, which may be adopted in industry. The article studies induction motors with incipient interturn fault severity with many well-known techniques. The experimental results prove many methods unreliable and insensitive to low level interturn fault detection. Finally, the authors propose a novel method that relies on the monitoring of the stray flux at three positions of the machine.

In this communication, we present a method to measure the thickness of transparent media employing a low coherence interferometer and a multi-element array as a photo-detector. The multi-element array employed is part of a consumer-grade digital camera (< 0.5 k$). A two-beam interferometer is created by inserting the slab of a transparent material half-way through into the measurement beam. The method is evaluated on a thin microscope cover slip and on a thicker microscope glass slide.

In this communication, we evaluate the suitability of Master-Slave (MS) optical coherence tomography (OCT) for processing of interferograms generated by an interferometer driven by an akinetic, electrically-tunable swept source from Insight with an ultra-large instantaneous coherence length. The akinetic source is programmed to sweep linearly, but within the sweep, at predictable times, the laser tuning introduces invalid regions in the interferogram, which are normally removed post-acquisition using a pre-calibration file. This makes sure that any optical frequency component is used once only and enables correct operation of a Fourier transform (FT). A FT applied to an unprocessed emitted spectrum leads to wide and numerous peaks in the A-scan. MS processing was introduced to avoid the necessary corrections demanded by conventional FT signal processing or its derivatives. The MS procedure consists of comparing photo-detected signals at the output of two interferometers, a Slave and a Master interferometer. The MS method was advanced along two avenues, either by using (i) electricallygenerated master signals (making use of the same interferometer twice) or (ii) optically-generated master signal via a recently introduced MS down-conversion procedure. We apply both avenues to the Insight source. Approach (i) tests the MS principle as an alternative to the Insight file correction while (ii) demonstrates near coherencelimited operation at a large axial range (>80 mm) for which a too-high sampling rate digitizer would have been needed. In this communication, we evaluate for the first time the suitability of the MS procedure to OCT measurements performed with the akinetic swept source commercialized by Insight. Two modalities are evaluated to implement the MS processing, based on: (i) digital generation of the master signals using the OCT interferometer and (ii) down conversion using a second interferometer driven by the swept source.

Conventional Finite-Control-Set Model Predictive Torque Control (FCS-MPTC) suffers from the high computational burden and the weighting factor tuning effort, which increase the flux and torque ripples and have a negative impact on the drive performance. Accordingly, this paper presents an enhanced FCS-MPTC for Permanent Magnet Synchronous Motor (PMSM) drives with reduced computational effort and without the use of weighting factors. Based on the use of a new 2-D lookup table (LUT) of Direct Torque Control (DTC) and different from prior method using eight predicted voltage vectors in the cost function, only three voltage vectors are predicted and evaluated, which reduce notably the computational effort. Furthermore, with the aim to eliminate the weighting factors in the cost function, the torque and flux vector references are converted into an equivalent angle between the stator and rotor flux vectors, which decreases the current and flux ripples and improves the control performance. Simulation results are presented to show the effectiveness of the proposed control method.

Most of the state-of-the-art LED drivers employed in lighting applications adopt current control strategies that rely on current sensing resistors. In multi-string LED lighting systems, commonly based on the single inductor multiple output (SIMO) topology, a current sensing resistor is typically inserted in each string, allowing to precisely control the current flowing through each string. This current control approach presents critical drawbacks: 1) the overall energy conversion efficiency is seriously affected by the fairly high number of current sensing resistors; 2) the system complexity is enhanced, as each LED string requires a current control loop; 3) the lifetime of both LEDs and drivers suffers an important depreciation due to the additional power losses incurred by the current sensing resistors. To overcome such drawbacks, this paper proposes a sensorless current control strategy suitable for LED drivers operated at continuous conduction mode (CCM), feeding multi-string LED lighting systems, which obviates the requirement of individual string current control. The proposed control strategy is implemented and validated on a fault-tolerant SIMO LED driver.

Under abnormal electrical supply conditions, induction motors can easily reach an overheating condition. A continuous operation under thermal stress significantly decrements the motors useful lifetime. In this paper a short-time thermal transient analysis, based on a Lumped Parameter Thermal Network (LPTN), is performed in order to evaluate the thermal behaviour of an asynchronous machine operating under supply voltage unbalance. Three types of supply unbalance are considered in this paper: unbalanced voltage amplitude, unbalanced phase, and a combination of both. The analytical model is used to estimate the temperature in different points of the stator. This model presents a reasonable compromise between simplicity, accuracy, and rapidity. The obtained results are validated using an experimental prototype.

Stator electrical faults are considered the most severe and challenging to detect among the various induction motor faults. This is due to the fast evolving severity level that leads from an early inter-turn fault to the machine breakdown. Many works have been published over the years presenting a variety of diagnostic techniques to detect this fault. However, the fault level severity is kept high enough to allow for the diagnosis neglecting the fact that at that severity level the machine will fail and thus diagnosis of the fault is useless. This paper challenges the existing technical know-how in the subject, while attempting to detect the fault at very low severity levels. It will be shown with extensive experimental testing and analysis that many well established methods are completely unreliable for this task. Finally, the authors propose a novel method that is able not only to detect the fault reliably but is also sensitive to the fault level severity.

Aluminum electrolytic capacitors (AECs) are widely used in the DC link of power converters, such as the three-phase interleaved boost converter (IBC) which offers many advantages over the conventional amplifier converter. IBCs can operate both in closed- or open-loop systems and any fault in the converter components can reduce significantly the overall system performance. AECs failures represent the major cause for power electronics equipment breakdown, mainly due to both aging and temperature effects involving significant increase on their equivalent series resistance (ESR) parameter. This reveals the importance of developing robust control strategies that allow evaluating the electrolytic capacitor state condition and keeping, at the same time, the performance of the converter controller, even under a capacitor fault occurrence. For that purpose, a fault detection and control strategy is proposed in this paper, for a three-phase interleaved boost converter application. The control task of this strategy uses a mixed sensitivity $\mathbf{H}\infty$ controller to ensure fast dynamics and robustness even under failure mode operation, while the fault detection task uses the Short Time Least Square Prony's (STLSP) method to perform an online estimation of the ESR parameter, allowing a continuous evaluation of the electrolytic capacitor state condition, and consequently avoiding a total system failure. The effectiveness of the proposed strategy is verified by several experimental tests.

Bearing fault is the most causes of machine breakdowns. Consequently, the monitoring of this component is a key point to increase the reliability, security and avoiding serious damage in machine. Vibration signal is widely used for diagnosis which is considered as a powerful tool for detecting mechanical defects. In this paper, a rolling bearing fault-diagnosis method based on variational mode decomposition (VMD) and artificial neural network (ANN) is proposed. First, the processing methodology of bearing diagnosis starts with the decomposition of the vibration signal by VMD technique into a set of intrinsic mode functions (IMFs). According to the aim of fault diagnosis, the selected fault indicator is calculated from the energy related to the most sensitive IMFs to the bearing defect. Second, the extracted feature is then used as input to the ANN. the proposed approach is then validated using data from the bearing data center of Case Western Reserve University. The results prove the efficient of this method which is able to discriminating from four conditions of rolling bearing, namely, normal bearing and three different types of defected bearings: outer race, inner race, and ball.

The communication refers to a solution to repetitive change of focus when performing swept source (tunable laser) interferometry. There are now swept source (SS) lasers exhibiting several meters coherence lengths for robotic navigation and cubic meter OCT. However, micron lateral resolution can only be achieved with sufficient high numerical aperture interface optics, in which case the depth range falls below sub-millimeter. Repetition of data collection is needed for each new focus (Gabor). This counteracts the advantage of SS-OCT, that of delivering information from all depths in one scan via a Fourier Transform (FT). To eliminate the time wasted on producing data from all axial range, Master Slave (MS) OCT is proposed, that delivers data while laterally scanning the beam, from a single depth of interest, in real time. We present combination of MS-OCT with 4 repetitions of acquisitions each for a different focus position, to acquire high resolution volumes and en-face OCT from different targets. By combining the two techniques, Gabor filtering and Master/Slave-OCT, a powerful imaging instrument is demonstrated. The MS technique allows simultaneous display of three categories of images in one frame: multiple depth en-face OCT images, two cross-sectional OCT images and a confocal like image obtained by averaging the en-face ones. We also demonstrate the superiority of MS-OCT over its FT based counterpart when used with a Gabor filtering OCT instrument in terms of the speed of assembling the fused volume.

Contains fulltext : 206779.pdf (Publisher’s version ) (Open Access) BACKGROUND: The objective of this study was to assess the cumulative incidence of invasive candidiasis (IC) in intensive care units (ICUs) in Europe. METHODS: A multinational, multicenter, retrospective study was conducted in 23 ICUs in 9 European countries, representing the first phase of the candidemia/intra-abdominal candidiasis in European ICU project (EUCANDICU). RESULTS: During the study period, 570 episodes of ICU-acquired IC were observed, with a cumulative incidence of 7.07 episodes per 1000 ICU admissions, with important between-center variability. Separated, non-mutually exclusive cumulative incidences of candidemia and IAC were 5.52 and 1.84 episodes per 1000 ICU admissions, respectively. Crude 30-day mortality was 42%. Age (odds ratio [OR] 1.04 per year, 95% CI 1.02-1.06, p < 0.001), severe hepatic failure (OR 3.25, 95% 1.31-8.08, p 0.011), SOFA score at the onset of IC (OR 1.11 per point, 95% CI 1.04-1.17, p 0.001), and septic shock (OR 2.12, 95% CI 1.24-3.63, p 0.006) were associated with increased 30-day mortality in a secondary, exploratory analysis. CONCLUSIONS: The cumulative incidence of IC in 23 European ICUs was 7.07 episodes per 1000 ICU admissions. Future in-depth analyses will allow explaining part of the observed between-center variability, with the ultimate aim of helping to improve local infection control and antifungal stewardship projects and interventions.

The ever-increasing evidences showing the benefits related to the transition to a more sustainable framework of energy distribution at buildings, based on DC microgrids, calls for the development of suitable technologies. Residential lighting systems based on LED technologies gain further significance as these technologies become mature. Unfortunately, power electronic technologies used to drive LED lighting systems are unable to correspond with the longevity levels of LED devices. Particularly, active semiconductors pose one of the major hurdles to the full exploitation of the LED lifetime. Accordingly, the development of reliable LED driving systems, capable of fully exploiting the lifetime of LEDs, becomes critical. Keeping in mind that adoption of DC microgrids at homes and offices is a scenario that is rapidly taking shape, it is important to develop power conversion solutions for such end. This paper proposes a fault tolerant LED driving system, based on a DC-DC converter, suitable for residential DC microgrids.

Induction motors airgap-eccentricity fault detection has attracted the interest of many researchers in the last decades. The discrete Fourier transform (DFT) has been widely used for that purpose. However, DFT can only give meaningful information for stationary signals. In addition, DFT requires a long acquisition time in order to get a high-frequency resolution. In this paper, an efficient time-domain technique based on a modified Prony's method for the airgap-eccentricity fault detection in induction motors is presented in order to overcome the DFT problems. Using this technique, the stator current and apparent power—as processed signals—are divided into short overlapped time windows and each one is analyzed by the least squares Prony's method. The proposed technique allows tracking the frequency and amplitude of the airgap-eccentricity fault characteristic component with a very high accuracy using only few data samples. A fault severity factor based on the amplitude of the estimated component is defined. The effectiveness and accuracy of the proposed method are verified through the presented simulation and experimental results.

Sustainability has become a major focus of the concrete industry, which is largely due to the CO2 emissions associated with Portland cement production. The process of crushing rocks to produce aggregates can also cause environmental damage since it generates stone powder, which is disposed of in the environment as waste material. Therefore, replacing cement with stone powder to reduce CO2 emissions during concrete production is an attractive alternative to sustainability. The use of high-strength concrete (HSC) appears to be another alternative since higher compressive strength results in lower CO2 emissions per MPa. In this context, the objective of the present work is to design a low-cement HSC via the partial replacement of Portland cement with stone powder and silica fume optimized using particle packing methods. The design approach selected consists of first designing the paste, followed by the design of the granular skeleton. Concretes were produced by varying the paste contents from 27 to 37% and the water/fines (w/f) ratio from 0.28 to 0.40. The efficiency of the HSCs was measured in the context of sustainability in terms of cement consumption and CO2 emissions, in addition to the properties of the fresh and hardened states. Results show that the most efficient composition of the paste was 64% Portland cement, 16% silica fume and 20% stone powder. The aggregate composition of 47% limestone sand, 30% gravel with a maximum particle size of 9.5 mm and 23% gravel with a maximum particle size of 19 mm presented the lowest void index. Respecting these material proportions, some concretes were designed with a compressive strength of 104 MPa using only 288 kg/m3 of cement. This represents a consumption of only 2.8 kg of cement/MPa of concrete compressive strength, which is less than the consumption reported by the literature for HSC (∼5 kg/m3/MPa) and results in a CO2 emissions/MPa reduction of over 44% in relation to concrete produced using mix design methods described in the literature. Furthermore, all of the low-cement HSC studied here presented high workability, excellent quality (according to the ultrasonic pulse velocities (above 4500 m/s)) and insignificant corrosion risk (based on the electrical resistivity test (higher than 100 KΩcm)). These findings contribute to the production of sustainable concretes since waste material can be used while simultaneously reducing greenhouse gas emissions.

As the main workforce of the global industry, it is fundamental to clearly understand all failures modes that may potentially deteriorate induction motors. Condition monitoring methodologies based on the thermal analysis of induction motors have tremendous potential as a health monitoring tool of any electric motor technology. In addition to the intrinsic benefits related to a non-invasive diagnostic technique, thermal analysis provides suitable information for the early detection of a plethora of fault scenarios. One of the fault modes which remains fairly unexploited in the literature is the short-circuit fault between turns of the stator windings. To assess the effects of such faults in the temperature of the stator windings of an induction motor, this paper develops a thermal model of the induction motor under study, resorting to the Finite Elements Method (FEM). To develop the FEM model, the simulation tool Flux2D (Cedrat) is employed. Distinctive fault severity levels are considered through the variation of the short-circuit resistance.

Fault detection and fault accommodation, as well as fault tolerance, are important issues in closed-loop controlled three-phase converters. For such systems, power semiconductors and sensors are the most affected components by the occurrence of failures. Therefore, fault diagnosis and remedial operating strategies involving such components are highly required. In this paper, a new reliable approach is proposed, which aims to diagnose current sensor faults and power semiconductor open-circuit faults in permanent magnet synchronous motor drives. The proposed fault diagnosis scheme uses only the measured currents, which makes it suitable for real-time implementation. The performance of the proposed technique is analyzed through experiments., Santander Totta under fellowship BIPD/ICI-FE-Santander Universidades - UBI/2016.

In this Letter, we propose a beam-shifting optical coherence tomography scheme for speckle reduction and blood flow rate calculation, where variations of the speckle pattern and Doppler angle were generated by parallel shifting of the sample beam incident on the objective lens. The resultant optical coherent tomography images could then be averaged for speckle noise reduction and simultaneously analyzed for flow rate measurement. The performance of the proposed technique was verified by both phantom and in vivo experiments.

Low manufacturing cost and high reliability make the induction machine suitable for different constant and variable speed applications. For machines operating in hazardous environments, the fully enclosed type is used, with limited access to the stator and rotor. Indirect air cooling method is usually employed with fins casing and an attached fan. Thus, the fan design is crucial as being the only resource to remove heat away from the machine. A poor thermal management of the electrical machine can lead to a machine failure and reduce the machine lifespan. Some machines are operating for bi-directional operation, which means the performance of the machine should be reviewed under both conditions. This paper focus on the impact of the fan cooling on the thermal profile of a 5.5 kW induction machine under bidirectional operation. Comparative studies using CFD simulations have been carried out to identify the effect of different fan types when operating at particular conditions. The performed work provides an understanding of the air flow under bi-directional operation, which notes the importance of the fan design and rotational direction in induction machines.

In this paper the occurrence of stator faults in line-start permanent magnet synchronous motors are analyzed. A dynamic model was developed in Matlab/Simulink and on-line fault diagnostic techniques are explored. To validate the presented approach, simulation results are compared with the motor experimental performance.

It has recently been shown that spectrum analysis of instantaneous power can provide sensitive online detection of rotor faults in induction motors compared with current, torque, speed, or vibration spectrum analysis. However, it was reported that monitoring of the twice slip frequency, $2sf_{s}$ , components induced by the fundamental component can produce false rotor fault alarms due to asymmetry in the rotor or low frequency load oscillations. In this paper, the rotor fault components induced in the power spectrum by the stator fifth and seventh space harmonics are derived to evaluate their immunity to false alarms. It is shown that the $(6 - 8s)f_{s}$ component can provide reliable detection of rotor faults under cases where existing methods produce false alarms. An experimental study performed on custom built rotor samples shows that the new components are capable of detecting rotor faults immune to false alarms produced by rotor axial air ducts, rotor anisotropy, and low frequency load oscillations for cases where existing methods fail. The components derived in this paper can also be applied to vibration, speed, torque, or acoustic monitoring for reliable detection of rotor faults.

Carbon nanotubes (CNTs) are carbon structures which take the shape of cylinders in nanometric scale. This work presents an evaluation in regard to the addition of CNTs in concrete made with Portland cement, focused on the importance of performing the CNTs dispersion in water ultrasound before its incorporation to the concrete mass. Therefore, three concrete mixtures were performed, one without CNT (reference series) and two with CNTs (one mixture with previous dispersion in water and additive using ultrasound and the other without dispersion). Then properties of fluidity, compressive and tensile strength and water absorption were analyzed. The amount of CNT added was 0.30% with respect to cement mass. In all cases, the previous dispersion of CNTs using ultrasound increased the effect of CNTs addition, evidencing the importance of the efficiency of such material when added to cement. Keywords: Carbon nanotubes; concrete; strength; water absorption. Nanotubos de carbono em concreto de cimento portland: Influencia da dispersao nas propriedades mecânicas e na absorcao de agua RESUMO Os nanotubos de carbono (NTCs) sao estruturas de carbono que obtem forma de cilindros em escala nanometrica. Este trabalho apresenta uma avaliacao da adicao dos NTCs em concreto de cimento Portland, com foco na importância da realizacao de dispersao dos NTCs a agua com uso do ultrassom antes de sua incorporacao a massa de concreto. Para isto, tres tracos de concreto foram preparados sendo um sem NTC (serie de referencia) e dois com os NTCs (uma serie com dispersao previa em agua e aditivo com o uso de ultrassom e outra sem dispersao). Analisou-se entao as propriedades de fluidez, resistencia a compressao, tracao e absorcao de agua. O teor de NTC adicionado foi de 0,30% em relacao a massa de cimento. Em todos os casos a dispersao previa dos NTCs usando o ultrassom potencializou o efeito da adicao de NTCs, mostrando-se importante para a eficiencia deste material, quando adicionado ao cimento. Palavras-chave: Nanotubo de carbono; concreto; resistencia; absorcao de agua. Nanotubos de carbono en concreto de cemento Portland. Influencia de la dispersion en las propiedades mecanicas y en la absorcion de agua RESUMEN Los nanotubos de carbono (NTC) son estructuras de carbono que se obtienen en forma cilindrica de escala nanometrica. Este articulo presenta una evaluacion de la adicion de NTC en hormigon de cemento Portland, centrandose en la importancia de llevar a cabo la dispersion de los NTC en el agua con el uso del ultrasonido antes de su incorporacion en la masa de hormigon. Para ello, tres mezclas de hormigon se prepararon con un NTC libre (referencia) y dos NTC (con una serie previa de dispersion en agua y el aditivo con el uso de ondas ultrasonicas y otras sin dispersion). A continuacion, se analizo las propiedades de fluidez, resistencia a la compresion, traccion y la absorcion del agua. El NTC anadio contenido de 0,30% a respecto de la masa de cemento. En todos los casos, la dispersion previa de NTC usando ultrasonido potencio el efecto de la adicion de nanotubos de carbono, siendo importante para la eficiencia de este material cuando se anade al cemento Palabras clave: Nanotubo de carbono; concreto; resistencia; absorcion del agua.