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    <title>Transport Research International Documentation (TRID)</title>
    <link>https://trid.trb.org/</link>
    <atom:link href="https://trid.trb.org/Record/RSS?s=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" rel="self" type="application/rss+xml" />
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    <language>en-us</language>
    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
    <docs>http://blogs.law.harvard.edu/tech/rss</docs>
    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
    <image>
      <title>Transport Research International Documentation (TRID)</title>
      <url>https://trid.trb.org/Images/PageHeader-wTitle.jpg</url>
      <link>https://trid.trb.org/</link>
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    <item>
      <title>On the Voltage Stress Reduction in Hairpin Windings: Guidelines and Critical Aspects</title>
      <link>https://trid.trb.org/View/2665524</link>
      <description><![CDATA[Transportation electrification roadmaps are pushing for a step-change increase in power densities of electric drives, leading to rapidly growing developments of high-switching frequency wide bandgap (WBG) semiconductor-based inverters. Meanwhile, induced high dV/dt can challenge the reliability of the stator winding insulation system. This study provides guidelines to mitigate the winding voltage stress through the implementation of an improved modular hairpin winding (HW) layout featuring a multibranch design, reconfigurable by simply reconnecting phase terminals and neutral points. This enables comparison of voltage distributions across different winding layout patterns. A high-frequency electrical lumped parameter network for the prediction of voltage stress distribution is further adopted, and validated through experimental tests carried out on different configurations. The downselected configuration reduces by 35% the maximum interturn voltage. Furthermore, sensitivity analyses at different rise times revealed that improvement could be limited to only 10%–15% when rise times are in the range of tens of nanoseconds. Under these conditions, the first series turns connected to the inverter side are very sensitive to sudden voltage spikes and experience the highest voltage stress, even though they have fewer connecting conductors between them and adjacent layers. In general, the article provides reliability-oriented HW design guidelines that address the integrity of the insulation system.]]></description>
      <pubDate>Tue, 02 Jun 2026 13:56:53 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665524</guid>
    </item>
    <item>
      <title>Framework for Insulation Thickness Calculation in PD-Free E-Machines for Automotive and Aerospace</title>
      <link>https://trid.trb.org/View/2665467</link>
      <description><![CDATA[This article presents a framework for optimizing insulation thickness (IT) in electrical machines (EMs), ensuring reliability and efficiency for a fixed copper diameter and slot geometry. A validated, model-based software, grounded in the streamer inception criterion (SIC), calculates optimal IT for turn-to-turn windings in automotive and aerospace applications, incorporating enhancement factors (EFs) from IEC 60034-18-41. IT is evaluated for automotive systems (1000 mbar) across five temperatures (20 °C–180 °C) and four inverter dc bus voltages (1–1.6 kV). Aerospace analysis considers three air pressures (600, 400, and 200 mbar) at altitudes of 13.8–38.6 kft, the same temperature range, and four voltage levels (0.7–1 kV). The framework is applicable to all winding topologies and evaluates IT under worst case conditions (nonimpregnated insulation) and varying partial discharge inception probabilities (PDIPs). Trends in partial discharge inception voltage (PDIV) versus IT are analyzed, with sensitivity to voltage variations examined across air pressures and temperatures. These findings support the design of reliable, high-performance insulation systems for electric transport.]]></description>
      <pubDate>Tue, 26 May 2026 11:56:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665467</guid>
    </item>
    <item>
      <title>Thermal behavior of road embankments and impact of snow in ditches</title>
      <link>https://trid.trb.org/View/2666550</link>
      <description><![CDATA[In cold climate regions, seasonal snow accumulation in road ditches plays a critical role in governing the thermal behavior of road embankments. Snow exerts a spatially uneven thermal influence on heat transfer within the embankment due to its strong insulating properties, which can lead to differential frost heave and the formation of cracks on the road surface. However, accurately quantifying this insulation effect requires detailed knowledge of the thermal regime of the snow cover accumulated in the ditches, including its temporal evolution throughout the winter season. Snow is a porous medium characterized by a high volume fraction of air, which significantly reduces the thermal conductivity of snow and provides a strong insulating capacity. This insulation creates a natural temperature gradient between the snow surface and its base, governing the rate of heat transfer through the snow. Once snow is deposited, a temperature gradient develops, initiating metamorphic processes that alter the morphology and bonding of the snow grains. These microstructural changes lead to temporal variations in the thermal conductivity of snow, making its accurate determination over time particularly challenging. Furthermore, freezing-melting cycles modify the content of unfrozen liquid water within the snow structure, which not only complicates the quantification of latent heat exchanges but also exerts a significant influence on the effective thermal conductivity. To address these challenges and gain a deeper understanding of the thermal dynamics in snow-covered road embankments, two experimental field sites were established in Luleå, Sweden.]]></description>
      <pubDate>Thu, 05 Feb 2026 08:33:45 GMT</pubDate>
      <guid>https://trid.trb.org/View/2666550</guid>
    </item>
    <item>
      <title>Peak-Hold-Aided Evaluation Approach for the Insulation State of Vehicle Cable Terminals via Adaptive Spatial–Temporal Graph-Gated Attention Networks</title>
      <link>https://trid.trb.org/View/2604020</link>
      <description><![CDATA[Existing assessment methods for vehicle cable terminals suffer from accuracy degradation due to insufficient ability to extract spatial and temporal features, and inability to be installed on resource-constrained high-speed electric multiple units (high-speed EMUs) due to huge parameters of the neural network model. A peak-hold-aided evaluation approach to acquire the insulation state of vehicle cable terminals via an adaptive spatial-temporal graph-gated attention network (AdaSTGGAT) is proposed in this article. Initially, an approach for the construction of temporal graph structures based on peak hold and Jensen-Shannon divergence is proposed to address the issues of large amounts of data and the difficulty of analyzing graph structures. The graph-gated attention block is subsequently introduced for feature extraction to extract the spatial-temporal features of the signal accurately. Furthermore, AdaSTGGAT is designed as the backbone for feature extraction and aggregation. Specifically, the supervision mechanism is introduced to stabilize the training process, which enables the model to be pruned. Ultimately, the proposed approach is experimentally validated via high-frequency current transformer (HFCT) experiments on vehicle cable terminals. The proposed methodology demonstrates robust spatial-temporal feature representation capabilities for insulation condition assessment for vehicle cable terminals, achieving average performance metrics of 97.40% accuracy, 97.50% precision, 97.40% recall, 97.40% F1-score, and 96.90% Kappa coefficient. Notably, the architecture incorporates a data-driven dynamic pruning mechanism that optimizes model complexity while maintaining diagnostic reliability, thereby advancing the practical implementation of online insulation monitoring systems in industrial applications.]]></description>
      <pubDate>Wed, 10 Dec 2025 16:01:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/2604020</guid>
    </item>
    <item>
      <title>Investigation and Mitigation of Insulated Joint Electrical Failure: A Guide</title>
      <link>https://trid.trb.org/View/2628405</link>
      <description><![CDATA[This report provides information on how to identify arcing at insulated joints (IJs), methods to diagnose the contributing factors, underlying causes, strategies for investigating IJ failures, and examples of how others have mitigated arcing. This guide was developed by conducting a literature review and an industry survey and identifying gaps and needs in the current state of knowledge. The guide’s purpose is to supply electrified railway operators and maintenance personnel with the information they need to operate, maintain, design, and modify their electrical railways.]]></description>
      <pubDate>Tue, 02 Dec 2025 13:46:35 GMT</pubDate>
      <guid>https://trid.trb.org/View/2628405</guid>
    </item>
    <item>
      <title>Thermal Influence of Physical Parameters of Additively Manufactured Windings in Permanent Magnet Synchronous Motors</title>
      <link>https://trid.trb.org/View/2603953</link>
      <description><![CDATA[For permanent magnet synchronous motor (PMSM), additively manufactured (AM) windings with variable cross-sectional shapes offer significant advantages in enhancing the slot fill factor and thermal properties, thereby contributing to an increase in power density. This article presents a thermal model for AM windings of PMSM that accounts for the anisotropy of the equivalent insulation thermal conductivity at various locations within the slot. This model improves the accuracy of the predicted winding temperature rise. The physical parameters of AM windings can be controlled by modifying the printing parameters and postprocessing conditions. The impact of electrical conductivity, thermal conductivity, and winding insulation parameters on the losses and temperature rise of PMSMs at various frequencies is then investigated. Finally, the temperature rise characteristics of the prototype PMSMs with the AM windings and the conventional windings are tested and compared, thereby confirming the validity of the thermal model for AM windings as well as their superior thermal properties.]]></description>
      <pubDate>Mon, 24 Nov 2025 10:24:54 GMT</pubDate>
      <guid>https://trid.trb.org/View/2603953</guid>
    </item>
    <item>
      <title>Effects of Partial Discharge Echo in Motor-Insulation Systems of Transportation Power Devices</title>
      <link>https://trid.trb.org/View/2553515</link>
      <description><![CDATA[One of the mostly applied assessments of electrical insulation’s condition is based on the measurement of partial discharges (PDs). In addition to conventional PD measurements on motor insulation, a novel approach called PD echo (PDE) is described in this article. This can be applied to various excitation-voltage waveshapes [such as sinusoidal, pulse wave modulated (PWM), etc.] that form chopped sequences. The PDE methodology may extract information about the condition of the insulation—especially depicting its surface effects. Since it operates in the voltageless part of a chopped sequence, it is more immune to excitation-driven disturbances. This article presents the results that were obtained on twisted pair (TP) specimens that were the representative of electrical-machine insulation that is untreated and degraded by hot-air streaming. A comparison of the experimental results based on the PDE time constant revealed distinct echo patterns (especially the accelerated decay of the PDE pulse magnitude) in cases of deteriorated TP samples. The echo discharges were attributed to the mechanisms that occurred on the enameled wire surface in the air gap between the turns. The aim of this article was to provide quantitative insight into the winding interturn insulation in the form of PDE attributes. It also provides an attempt to extract additional insulation degradation-related information from phase-resolved PD images. The PDE phenomenon may open new opportunities for evaluating electrical insulation and providing directions toward potential diagnostic applications in motors.]]></description>
      <pubDate>Mon, 23 Jun 2025 15:54:47 GMT</pubDate>
      <guid>https://trid.trb.org/View/2553515</guid>
    </item>
    <item>
      <title>Multiple Fault Diagnosis of PMSM Based on Stator Tooth Flux and Parallel Residual Convolutional Neural Network</title>
      <link>https://trid.trb.org/View/2512098</link>
      <description><![CDATA[Interturn short circuit fault (ISF), insulation fault (INF), eccentricity fault (ECF), and demagnetization fault (DMF) are the most common faults in permanent magnet synchronous motor (PMSM). As these faults degrade reliability and cause serious catastrophes, it is necessary to diagnose these faults. However, in current methods, a fault indicator (FI) can often diagnose only one or two faults, which means that multiple FIs are required for diagnosis above four faults. To diagnose multiple faults with fewer FIs, a fault diagnosis method based on stator tooth flux (STF) of multiple teeth and multiscale kernel parallel residual convolutional neural network (PR-CNN) is proposed in this article. First, the STF of multiple teeth under four faults is analyzed. Then, FI is proposed based on the characteristics of the STF. Finally, the proposed PR-CNN is compared with state-of-the-art convolutional neural networks (CNNs) highlighting the superiority of this application. The results indicate that the proposed method can diagnose the above four faults by a single FI with an accuracy of 98.8% and a training data ratio of 40%. This work provides a significant reference for the multiple fault diagnosis of PMSM.]]></description>
      <pubDate>Thu, 05 Jun 2025 13:59:01 GMT</pubDate>
      <guid>https://trid.trb.org/View/2512098</guid>
    </item>
    <item>
      <title>Prediction of Breakdown Time of Insulation Material for Use in Medium-Voltage Inverter-Fed Marine Propulsion Motor Applications</title>
      <link>https://trid.trb.org/View/2511887</link>
      <description><![CDATA[Large voltage transients and high frequencies from power electronic inverters are the major cause and concern for insulation failure within inverter-fed machines. This is especially true as more wide bandgap devices and electric motor drives penetrate various applications, including renewable integration. To understand the impact of high-voltage and high-frequency of emerging power electronic inverters on insulation lifetime, a medium-voltage H-bridge inverter testbed was built to stress Kapton HN (polyimide) films. These films of different thicknesses were subjected to voltage endurance tests at different inverter voltages and frequencies to evaluate their breakdown time. Three different machine learning (ML) regression algorithms—linear, random forest, and support vector machine (SVM)—were employed on time to breakdown data to predict the insulation lifetime. Results show that random forest regression performs best and gives a reasonably accurate prediction of time to failure of Kapton HN film given its thickness at any inverter voltage and switching frequency tested. In addition, a closed-form equation of insulation breakdown time is derived from the linear regression to predict breakdown time for various insulation thicknesses, under varying inverter voltage, and inverter switching frequency.]]></description>
      <pubDate>Fri, 23 May 2025 15:34:44 GMT</pubDate>
      <guid>https://trid.trb.org/View/2511887</guid>
    </item>
    <item>
      <title>Insulating Materials for Electrical Components Used for Power Transmission on Board the Aircraft</title>
      <link>https://trid.trb.org/View/2511826</link>
      <description><![CDATA[Extensive efforts are devoted to the electrification of aircraft by introducing higher electrical power levels. Accordingly, the electrical components, wires and interconnects, are being increasingly applied on- board, and their insulations are inexorably facing heightened challenges of higher electric stresses, more stringent installation conditions, and a wide variety of environmental constraints. It could lead to multiple insulation aging patterns, entailing various failure modes. Thus, the insulation has been seen as a pivotal element in every on- board electrical component and equipment since its current performances could govern the on- board voltage rating. Here, the authors first drew up the constraints facing such insulations before specifying the criteria governing their selection. Then, they reviewed in detail the high-performance insulations used, and those that are intended to be potentially used, for electrically isolating the aeronautical components employed for power transmission. The aim is to elucidate the limits of the current insulations in respect of the aforementioned constraints and to identify the merits of the candidate ones. This review does not only provide a broad assortment of key knowledge on insulating materials, much sought after by component designers, manufacturers, and engineering researchers but also reveals for the scientific polymer community the issue of electrically insulating aeronautical components.]]></description>
      <pubDate>Mon, 28 Apr 2025 08:50:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/2511826</guid>
    </item>
    <item>
      <title>SiC-MOSFET-Based High Voltage Pulse Generator for Testing Motor Insulation Used in EVs</title>
      <link>https://trid.trb.org/View/2511373</link>
      <description><![CDATA[The use of wide bandgap (WBG) power semiconductor devices in the transportation electrification area is gaining increased interest due to high power density, low power losses, high switching frequencies, and high operating temperatures. In specific, power electronics-based converters play a crucial role in driving the motors employed in the transportation area. However, concerns arise regarding motor insulation when employing WBG switching devices due to their fast rise time and high-frequency characteristics. These characteristics can place significant stress on the motor insulation, potentially causing premature failures. As such, it is essential to investigate motor insulation under the operation of WBG-based power converters. In this work, a high voltage (HV) pulse generator is developed specifically for studying the motor insulation of electric vehicles (EVs). The proposed system incorporates a converter based on SiC-MOSFETs, offering flexibilities with pulse amplitude, frequency, duty cycle, rise time, overshoot, and wave shape. The design and functionality of the proposed generator are evaluated through both MATLAB Simulink simulations and experimental results.]]></description>
      <pubDate>Thu, 27 Mar 2025 11:35:31 GMT</pubDate>
      <guid>https://trid.trb.org/View/2511373</guid>
    </item>
    <item>
      <title>Energy saving strategies for electric vehicles operating in cold climates</title>
      <link>https://trid.trb.org/View/2491240</link>
      <description><![CDATA[Electromobility has gained significance over recent years in an attempt to reduce greenhouse gas emissions contributing to climate change. The requirements for the performance and efficiency of electric vehicles are high to make them an attractive alternative to conventional fossil-fuel-driven vehicles. Lithium-ion batteries are excellent energy storage systems when operated under conducive conditions, i.e. a temperature range of 15°C to 35°C. Their performance and cycling life are drastically affected when operated outside this range. In cold climates, the battery packs need to be heated for optimal performance. Additionally, the passenger cabins must be climatized. The energy for battery and cabin heating is derived from the packs, which consequently results in reduced driving range. This work is concerned with strategies for reducing these heating loads. Three methods, namely cabin insulation, cabin air recirculation, and battery pack thermal encapsulation, have been investigated to estimate heating load reductions and their influence on vehicle range. Cabin insulation was investigated on a passenger car cabin and a truck cabin using computational fluid dynamics (CFD). Insulating the cabin reduced the heat losses, heating the cabin faster and to higher mean temperatures than the non-insulated configuration under a constant heating load. An adaptive cabin air recirculation strategy was used to control the return-air ratio such that window fogging was avoided, and good air quality could be maintained. Numerical simulations using a coupled CFD-thermoregulation model were performed on the truck cabin with cabin heating and recirculation controllers. Combining the two strategies (cabin insulation and air recirculation) further decreased the cabin heating energy consumption.]]></description>
      <pubDate>Fri, 17 Jan 2025 15:17:04 GMT</pubDate>
      <guid>https://trid.trb.org/View/2491240</guid>
    </item>
    <item>
      <title>Thermal insulation of the combustion chamber in a light duty diesel engine</title>
      <link>https://trid.trb.org/View/2491238</link>
      <description><![CDATA[Reduction of heat loss from the combustion chamber in an engine has great potential to decrease fuel consumption and CO2 emissions. Research on thermal barrier coatings (TBC) has been performed since the early eighties to address this potential. However, reported results for engine efficiency improvements with insulation show a large spread and there is no consensus on the actual benefits of TBCs. The purpose of this PhD project was to make an accurate assessment of state-of-the-art TBCs and establish what coating properties are required to improve indicated engine efficiency. Cylinder pressure data and measured heat losses to the piston cooling oil in a light duty single cylinder engine formed the basis for the experimental research. A robust and automated measurement method was developed and combined with statistical modeling of the data. Plasma sprayed yttria stabilized zirconia and anodized alumina were selected to establish the effectiveness of state-of-the-art TBCs. These coatings, applied on the piston top, did not improve indicated efficiency. The high surface roughness of the coatings was an important contributor to the poor performance. Experiments with a novel coating technology: suspension plasma spraying and a new material gadolinium-zirconate, led to a slightly improved indicated efficiency. Details in the heat release analysis indicated that the high open porosity in this coating might lead to increased heat losses and fuel entrainment. An investigation of possible charge entrainment effects in a standard plasma sprayed zirconia thermal barrier coating was performed, using a combination of engine experiments, CFD simulations and a 0D crevice model. The crevice model predicted the observed deviations of the apparent rate of heat release surprisingly well, which is strong evidence for the existance and significance of this crevice effect.]]></description>
      <pubDate>Fri, 17 Jan 2025 15:17:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/2491238</guid>
    </item>
    <item>
      <title>Dynamic Distribution of Rail Potential with Regional Insulation Alteration in Multi-Train Urban Rail Transit</title>
      <link>https://trid.trb.org/View/2448750</link>
      <description><![CDATA[Rail potential (RP) has become a disaster for the safe operation of metro lines. In urban rail transit (URT), regional insulation degradation often occurs due to the harsh environment of the reflux conductor for traction current, leading to the complex distribution of RP. In this paper, the dynamic distribution of RP with regional insulation alteration in URT is studied. First, the distribution model of the reflux system with regional insulation alteration is established. Second, utilizing the distributed parameter element method and taking into account the constraint conditions of the concentrated parameters, a superposition calculation method of RP in the reflux system is proposed. Finally, using Guangzhou Metro as an example, the simulation of different insulation states in long and local areas of URT is carried out. Results show that the RP amplitude decreases while the stray current amplitude increases when the insulation is degraded. At the same time, when the insulation in the local area degrades, the RP at the far end increases.]]></description>
      <pubDate>Thu, 21 Nov 2024 09:25:28 GMT</pubDate>
      <guid>https://trid.trb.org/View/2448750</guid>
    </item>
    <item>
      <title>Use of Isotemp Curves for Selecting Automotive Cable</title>
      <link>https://trid.trb.org/View/1786786</link>
      <description><![CDATA[The thermal lifetime of cable used in automobiles can be predicted using Isotemp Curves. These curves take into account the cumulative effects of both temperature rise due to current flow as well as ambient temperature. Use of these curves allows for the proper selection of an insulating material and cable size based on identified electrical load, environmental conditions, and desired product life.]]></description>
      <pubDate>Fri, 01 Nov 2024 09:56:09 GMT</pubDate>
      <guid>https://trid.trb.org/View/1786786</guid>
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