Hairpin windings for high reliability and high power density electrical machines

In the last years the increasing demand of higher torque and power densities has led to the adoption of hairpin windings (HWs) in electrical machines, mainly in those intended for automotive applications. However, this winding topology is quite sensitive to AC losses, hence one of their main challenges is represented by their reduction. This work deals with different design aspects related to the enhancements of some performance figures of rotating electrical machines for traction applications, above all power density and reliability, mainly through the adoption of HWs.In the last years the increasing demand of higher torque and power densities has led to the adoption of hairpin windings (HWs) in electrical machines, mainly in those intended for automotive applications. However, this winding topology is quite sensitive to AC losses, hence one of their main challenges is represented by their reduction. This work deals with different design aspects related to the enhancements of some performance figures of rotating electrical machines for traction applications, above all power density and reliability, mainly through the adoption of HWs

Analysis of Voltage Distribution and Connections within a High-Frequency Hairpin Winding Model

In the last years the adoption of hairpin windings is increasing, especially in the automotive sector, mainly due to their inherently high fill factor and electric loading capability. A critical aspect related to the reliability and lifetime of every winding typology is the voltage stress due to the uneven voltage distribution. This phenomenon has already been largely analyzed in conventional stranded conductors, while a few studies are available for hairpin windings. With the spreading of wide bandgap devices, the investigation on voltage distribution becomes an ever-timely topic due to their short rise times. This paper presents an analysis of the uneven voltage distribution triggered within hairpin windings by a low rise time waveform, using a complete high-frequency winding model. The different options to series-connect different paths are investigated, providing simple but essential guidelines to reduce the electrical stress within hairpin windings. © 20XX IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksThis paper reflects only the author's view. JU is not responsible for any use that may be made of the information it contains

Collegamento Ferroviario Aeroporto – Stazione centrale di Olbia: una prima sperimentazione di sensoristiche integrate da drone in VPIA

Constant detection and monitoring of archaeological sites has always been an important national goal for many countries, which recognize fundamental the prior identification of archaeological evidence buried for the preservation of heritage. Since the first applications, archaeologists have grasped the potential of using drones to automate data collection of exposed archaeological evidences. But now the technological evolutio allowed to see archaeological buried structures below the ground surface. Until recently, real great obstacle is envisioned by high cost and technical barriers represented by large-scale data implementation and collection. The recent advances in thermal imaging, depth imaging, drones and artificial intelligence technology have reduced costs and improved the quality and volume of data collected and processed. This article proposes a case study where different sensors were combined for the archaeological evaluation of a large area

Partial Discharges in Electrical Machines for the More Electric Aircraft—Part I: A Comprehensive Modeling Tool for the Characterization of Electric Drives Based on Fast Switching Semiconductors

This paper proposed a modelling approach for the comprehensive analysis of high-frequency challenges in electrical drives designed for aerospace applications, in particular the overvoltage at the machine terminals and the voltage distribution within windings. After a separate description of the models for the estimation of these insulation stress sources, the combined model was detailed. The main benefit of developing a combined, flexible and comprehensive tool is that both overvoltage at machine terminals and uneven voltage distribution can be calculated simultaneously, without neglecting the voltage overshoot when estimating the voltage distribution (and vice versa). In fact, an accurate calculation of the terminal overvoltage is necessary to provide a good estimation of the voltage within winding turns since its waveform shape can be quite different with respect to the converter output, even with cables of a few meters. A case study based on a real aerospace application was considered to investigate the model validity and accuracy. Experimental results were performed on a complete system comprising a SiC-based converter, a connecting cable and a machine stator, proving the simulation model accuracy in terms of peak voltages of both the line-to-line terminal voltage and the turn voltage distribution across the first turns, which are the most relevant quantities for the sake of this study as well as for the investigations of the subsequent companion papers. In the forthcoming papers, the effects of different rise times and cable lengths on the inception of partial discharges will be investigated through fast parametric simulation carried out using the proposed combined model. The feasibility of using conventional insulation systems for aircraft applications using SiC drives fed by a ±270 V DC bus voltage will be discussed, with the aim of signaling and finding solutions to improve the overall reliability

Effects of continuous positive airway pressure on comprehensive geriatric assessment and cognitive function in elderly patients with obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) can lead to cognitive impairment and depression affecting memory, attention, and executive functions. Continuous positive airway pressure (CPAP) treatment seems to be able to revert changes in brain networks and neuropsychological tests correlated to OSAS. The aim of the present study was to evaluate the effects of a 6-month treatment with CPAP on functional, humoral and cognitive parameters in a cohort of elderly OSAS patients with several comorbidities. We enrolled 360 elderly patients suffering from moderate to severe OSAS and indication for nocturnal CPAP. At baseline the Comprehensive Geriatric Assessment (CGA) revealed a borderline Mini-Mental State Examination (MMSE) score that improved after 6-month treatment with CPAP (25.3 +/- 1.6 vs 26 +/- 1.5; p < 0.0001), as well as the Montreal Cognitive Assessment (MoCA) showed a mild improvement (24.4 +/- 2.3 vs 26.2 +/- 1.7; p < 0.0001). Moreover, functionality activities increased after treatment, as documented by a short physical performance battery (SPPB) (6.3 +/- 1.5 vs 6.9 +/- 1.4; p < 0.0001). Reduction of the Geriatric Depression Scale (GDS) from 6.0 +/- 2.5 to 4.6 +/- 2.2 (p < 0.0001) was also detected. Changes of homeostasis model assessment (HOMA) index, oxygen desaturation index (ODI), sleep-time spent with saturation below 90% (TC90), peripheral arterial oxyhaemoglobin saturation (SpO(2)), apnea-hypopnea index (AHI) and estimation of glomerular filtration rate (eGFR), contributed, respectively, to 27.9%, 9.0%, 2.8%, 2.3%, 1.7% and 0.9% of MMSE variability for a total of 44.6% of MMSE variations. GDS score changes were due to the improvement of AHI, ODI and TC90, respectively, for 19.2%, 4.9%, 4.2% of the GDS variability, cumulative responsible for 28.3% of GDS modifications. The present real-world study shows that CPAP treatment is able to improve cognition and depressive symptoms in OSAS elderly patients

Performance improvement of SPM synchronous machines with non-conventional stator slot magnetic wedges

The opportunity to employ magnetic wedges in superficial permanent magnet machines with fractional-slot concentrated winding has been evaluated in this paper, with the aim to reduce the power losses, especially in the magnets, to increase the overall efficiency and to improve the field weakening capability. Finite element simulations with two different software are here presented, by using a model experimentally validated on a real motor. A novel wedge composed by different portions of materials with different values of magnetic permeability is proposed. The effects of both conventional and nonconventional magnetic wedges have been evaluated, in order to optimize the performance of the motor in all working conditions

Dv/Dt Filtering Techniques for Electric Drives: Review and Challenges

The use of wide band gap devices in power converters is becoming more and more popular since they enable operations at higher switching frequencies, voltages and temperatures compared to traditional power semiconductors, while also improving the efficiency. However, in electric drives, they also tend to increase voltage overshoots at motor terminals and to produce uneven voltage distributions across stator windings, due to their high rate of voltage change over time (dv/dt). In order to mitigate these issues, passive filters can be employed. The aim of this paper is to give an overview of possible solutions based on passive filters, analyzing the main advantages and drawbacks. A comprehensive, qualitative comparative study is carried out taking into account common mode currents reduction, power losses, costs, dimensions and reliability

On the AC Losses in the End Conductors of Hairpin Windings

In the last years, several resources have been employed to increase torque and power density values in electrical machines, especially in those intended for transport applications. In this context, the adoption of hairpin conductors is spreading thanks to their inherently high fill factor. Their main drawback is represented by their sensitivity to high-frequency phenomena, which can have a significant impact on the Joule losses and thus on the overall efficiency. While several researches have recently focused on ways to model and reduce such high-frequency losses in the slots, i.e. within the conductors’ active sides, a few data are available on their impact in the end winding regions. This work provides an investigation on the AC losses occurring in the end conductors of a hairpin winding traction motor. The losses are determined through 3D finite element simulations for a wide frequency range, and compared against those occurring in the active part of the machine. © 20XX IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksThis paper reflects only the author's view. JU is not responsible for any use that may be made of the information it contains

Effect of SGLT2-Inhibitors on Polygraphic Parameters in Elderly Patients Affected by Heart Failure, Type 2 Diabetes Mellitus, and Sleep Apnea

Obstructive sleep apneas (OSAs) and central sleep apneas (CSAs) are the most common comorbidities in Heart Failure (HF) that are strongly associated with all-cause mortality. Several therapeutic approaches have been used to treat CSA and OSA, but none have been shown to significantly improve HF prognosis. Our study evaluated the effects of a 3-months treatment with sodium-glucose cotransporter type 2 inhibitor (SGLT2i) on polygraphic parameters in patients with sleep apnea (SA) and HF, across the spectrum of ejection fraction, not treated with continuous positive air pressure (CPAP). A group of 514 consecutive elderly outpatients with HF, type 2 diabetes mellitus (T2DM) and SA, eligible for treatment with SGLT2i, were included in the investigation before starting any CPAP therapy. The two groups were compared with the t-test and Mann–Whitney test for unpaired data when appropriate. Then, a simple logistic regression model was built using 50% reduction in AHI as the dependent variable and other variables as covariates. A multivariate stepwise logistic regression model was constructed using the variables that linked with the dependent variable to calculate the odds ratio (OR) for the independent predictors associated with the reduction of 50% in AHI. The treated group experienced significant improvements in polygraphic parameters between baseline values and follow-up with reduction in AHI (28.4 ± 12.9 e/h vs. 15.2 ± 6.5 e/h; p p p 2 improved (91. 3 ± 2.3 vs. 93.8 ± 2.5); p < 0.0001. These benefits were not seen in the untreated population. The use of SGLT2i in patients suffering from HF and mixed-type SA not on CPAP therapy significantly contributes to improving polygraphic parameters