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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" />
    <description></description>
    <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>
    </image>
    <item>
      <title>Partial Discharge Prediction Model for Electric Motors with Enameled Flat Wire</title>
      <link>https://trid.trb.org/View/2734892</link>
      <description><![CDATA[Recent high-specific-power electric machines (EMs) in automotive applications operate at elevated voltages and in harsh environmental conditions. The resulting electrical and thermal stress makes the winding insulation system vulnerable to premature failure due to partial discharge (PD) activity. The main objective of this article is the development and validation of a generalized finite element model (FEM)-based PD prediction model for enameled flat wires that can be accurately applied to different winding geometries. The PD prediction model is simulated for different insulation thicknesses and relative permittivity values based on the Schumann criterion and the Townsend discharge mechanism. To ensure model fidelity, the influence of environmental factors such as temperature, cooling oil, and impregnation material on the PD inception voltage (PDIV) is studied. Moreover, different electrical stresses, including switching frequency, rise time, and overshoot factor (OF), are considered. The experimental results obtained in this article are fit with the proposed model. The findings obtained from the combined FEM and experimental results approach provide essential guidance for designing robust, reliable insulation systems for next-generation electric powertrain applications.]]></description>
      <pubDate>Fri, 25 Sep 2026 10:51:40 GMT</pubDate>
      <guid>https://trid.trb.org/View/2734892</guid>
    </item>
    <item>
      <title>Extended Numeric-Based Approach for the Selectivity Analysis of Vehicular Electronic Fuses in Case of a Thermal Wire Overload</title>
      <link>https://trid.trb.org/View/2734984</link>
      <description><![CDATA[The increasing requirements regarding functional safety lead to the integration of electronic fuses (eFuses) and their software-based thermal wire protection mechanism in novel vehicular power systems. As with melting fuses, to ensure the supply of safety-critical loads, the selective tripping of eFuses when clarifying a fault has to be guaranteed. In this article, an existing numeric-based method to calculate the triggering time of eFuses in case of a thermal wire overload is extended to consider the current measurement's quantization and the thermal protection of the eFuse itself in selectivity analyses. Besides that, approaches are shown to convert a measured load current profile into the values processed in the eFuse's control logic and, based on this, the ability of the extended method for selectivity analyses is proven by a validation. Using the method, the triggering time pursuant to state-of-the-art wire protection algorithms depending on the current profile passing the eFuse and depending on the eFuse's data acquisition (sampling, filtering, analog-to-digital converters (ADCs) quantization) is studied as well as aspects important regarding selectivity are identified, e.g., current profiles with high but short pulses cause smallest possible triggering times pursuant to the thermal wire protection mechanism.]]></description>
      <pubDate>Wed, 23 Sep 2026 15:56:09 GMT</pubDate>
      <guid>https://trid.trb.org/View/2734984</guid>
    </item>
    <item>
      <title>AC Copper Loss Reduction in Electrical Machines through Winding Transposition of Rectangular Bundle with Compressed Conductors</title>
      <link>https://trid.trb.org/View/2735080</link>
      <description><![CDATA[This article introduces an innovative novel winding structure optimization method, aiming to mitigate AC copper losses and preserve high copper fill factor in electrical machines simultaneously. By combining a rapid circulating current (CC) loss calculation method and finite element analysis (FEA), both the CC loss and eddy current (EC) loss are simultaneously suppressed in the winding composed of rectangular bundles with compressed conductors, leading to an effective reduction on overall AC copper loss. The FEA results demonstrate that the proposed winding structure can achieve a ratio of AC-to-DC copper loss of active length as low as 0.05 at 1000 Hz. Based on the calculation results, a motorette (composed of winding, stator, and rotor core) was fabricated, achieving 47% copper fill factor in a parallel-tooth slot and restricting the AC-to-DC copper loss ratio of active length to 0.13 at 800 Hz and 0.27 at 1000 Hz, respectively. Compared with Litz wire, the proposed winding demonstrates improvements in copper fill factor and limited compromise in AC copper loss suppression ability below 1000 Hz, thereby beneficial to power density enhancements in electrical machines.]]></description>
      <pubDate>Thu, 06 Aug 2026 09:22:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/2735080</guid>
    </item>
    <item>
      <title>An Overview of Aluminum Windings and Their Manufacturing Technologies in Electrical Machines</title>
      <link>https://trid.trb.org/View/2735096</link>
      <description><![CDATA[Due to its lower density and reduced cost, aluminum is increasingly adopted as a substitute for copper in lightweight and cost-effective winding applications. Its superior manufacturability further facilitates the realization of unconventional winding geometries, which contribute to enhanced loss suppression and improved cooling performance. To offer deeper insights, this article aims to provide a comprehensive review of aluminum windings in electrical machines, with a particular emphasis on their benefits in loss reduction and cooling enhancement. A comparative analysis of material properties of aluminum and copper is first conducted, followed by a summary of their unique effects on loss suppression and cooling performance. Finally, advanced manufacturing technologies and industrial applications of aluminum windings are briefly outlined. Moreover, a critical discussion is included to address their current limitations and highlight future development opportunities.]]></description>
      <pubDate>Tue, 04 Aug 2026 09:34:03 GMT</pubDate>
      <guid>https://trid.trb.org/View/2735096</guid>
    </item>
    <item>
      <title>Dynamic modelling of the stator system of flat wire motors</title>
      <link>https://trid.trb.org/View/2677528</link>
      <description><![CDATA[The dynamic behaviour of a stator system is crucial for the development of electric motors, as it plays a vital role in predicting and optimising the motor noise, which has emerged as a primary source of noise emissions in pure electric vehicles. Although the finite element method (FEM) is widely employed for modelling stator systems, existing FEM models typically focus on circular wire windings and fail to accurately represent stator systems with flat wire windings. Consequently, this paper aims to develop more precise FEM models for flat wire motor stator systems. The FEM models for the stator core, flat wire windings, insulating material, and the entire stator system are constructed by incorporating the unique characteristics of flat wire stator systems, particularly their radial stacking features. These proposed FEM models are validated through modal experiments conducted on an 8-pole 48-slot permanent magnet synchronous motor with flat wire windings.]]></description>
      <pubDate>Wed, 24 Jun 2026 13:22:07 GMT</pubDate>
      <guid>https://trid.trb.org/View/2677528</guid>
    </item>
    <item>
      <title>Method for Thermal Property Characterization From In Situ Measurements Applied to the Performance Evaluation of Electric Machine Windings</title>
      <link>https://trid.trb.org/View/2665602</link>
      <description><![CDATA[A combined experimental and model-based methodology is proposed for characterizing thermal properties of electric machine components, integrating assembly-level measurements, inverse modeling, and uncertainty quantification. Unlike traditional approaches, the method applies sensor weighting and assesses parameter identifiability, supporting improved measurement design. The methodology is demonstrated by quantifying maximum current density of five wire types—rectangular copper and aluminum, thick and thin stranded, and litz wires—using motorette setups. The proposed methodology minimizes the weighted mean absolute error (MAE) between model and experiment across all motorettes from 12.9 °C (literature properties) to 1.2 °C. Global uncertainty analysis reveals limited identifiability of core axial conductivity and winding–wedge interface resistance. Current densities, including skin and proximity effects, are simulated using fitted thermal properties. At low frequency, copper rectangular wires perform best (8.9 A/mm²), followed by aluminum (6.9 A/mm²), stranded thick (6.3 A/mm²), and stranded thin and litz wires (6.2 A/mm²). At 1 kHz, stranded thin and litz wires perform best (6.2 A/mm²), while aluminum rectangular (4.8 A/mm²), copper rectangular (4.2 A/mm²), and stranded thick wires (3.9 A/mm²) show reduced performance. Using literature thermal properties yields 1%–13% lower current densities. These results validate the methodology and highlight its value for uncertainty-aware thermal characterization, sensor placement, and quantitative electromagnetic–thermal wire performance assessment in machine design.]]></description>
      <pubDate>Wed, 17 Jun 2026 16:13:03 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665602</guid>
    </item>
    <item>
      <title>Hybrid Cross Section Flat Wire Winding and Layered AC Loss Suppression Method</title>
      <link>https://trid.trb.org/View/2659199</link>
      <description><![CDATA[To improve the power density of permanent magnet synchronous motors (PMSMs) for electric vehicles, round wire winding is gradually replaced by flat wire winding. The large cross-sectional area of the flat wire winding causes significant ac loss and temperature. AC loss includes the eddy current loss and dc loss. The eddy current loss in the high-frequency region needs to be suppressed, and the slot fill rate needs to be guaranteed to suppress the dc loss in the high-torque region. The loss distribution of different layer windings is affected by the distribution of magnetic leakage in the slot. The magnetic leakage is generated by the joint action of armature current and the permanent magnet. Based on the analysis of the causes of ac loss in different layers under various working conditions, this article proposes the layered loss suppression method (LLSM). The novel hybrid cross section flat wire winding (HCSW) is proposed based on the LLSM and verified by experiments. The results show that the loss of HCSW is reduced by 21.4% in peak speed working conditions and the slot fill rate is guaranteed. The area of the high-efficiency region is increased by 11% compared with the original model.]]></description>
      <pubDate>Tue, 26 May 2026 11:56:24 GMT</pubDate>
      <guid>https://trid.trb.org/View/2659199</guid>
    </item>
    <item>
      <title>Fluid Dynamic Modeling of Composite Oil-Cooled Motors With Flat-Wire Concentrated Windings</title>
      <link>https://trid.trb.org/View/2665462</link>
      <description><![CDATA[In the context of high-power-density applications, oil-cooled motors have emerged as a research focus due to their superior cooling performance. The optimized design of cooling structures and the development of fluid analysis methods are crucial for improving overall system performance. In this study, a composite oil-cooled structure with concentrated flat-wire windings is proposed to enhance heat dissipation capability. Based on this configuration, an innovative hydrodynamic modeling approach for the stator and rotor oil channels is developed, effectively addressing the low efficiency of conventional finite element simulations. Using the proposed modeling method, the internal flow nonuniformity of the oil-cooled motor is analyzed, revealing the mechanisms by which key structural parameters affect heat transfer nonuniformity. Finally, experimental results demonstrate that the proposed model provides accurate flow rate predictions. The prototype achieves a continuous current density of 33.6 A/mm², with a peak motor temperature of 130 °C—representing a 60.7% improvement compared to conventional oil-cooling solutions.]]></description>
      <pubDate>Tue, 26 May 2026 11:56:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665462</guid>
    </item>
    <item>
      <title>AC Loss Calculation for Litz Wire Windings in Electrical Machines</title>
      <link>https://trid.trb.org/View/2665449</link>
      <description><![CDATA[High-frequency operation of electrical machines leads to excessive ac losses in the windings due to skin and proximity effects. To mitigate these losses, multistrand windings or Litz wire windings can be employed. This article explores the applicability of the direct finite-element (FE) method and two computationally efficient approaches—the homogenization technique and the FE-based dB / dt technique—for predicting Litz wire ac losses in electrical machines. The experimental validation is conducted using a motorette model with different configurations. Based on the dB / dt technique, a fast sweep method is proposed for ac loss calculation across various Litz wire specifications. This method efficiently scales with variations in working points, enabling the optimal design of Litz wire over a working cycle to minimize winding losses in a computationally efficient manner.]]></description>
      <pubDate>Tue, 26 May 2026 11:56:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665449</guid>
    </item>
    <item>
      <title>Contact-Mechanics-Based Catenary–Pantograph Interaction Model for High-Speed Electric Railway Systems</title>
      <link>https://trid.trb.org/View/2591457</link>
      <description><![CDATA[This article introduces a contact-mechanics-based catenary–pantograph interaction model (HCM-M6) for use in high-speed electric railways in a finite element (FE) simulation framework. The contact boundary conditions are of Signorini nonlinear type, with exact constraint enforcement and no need for any predefined penalty spring. This also ensures automatic contact loss and reattachment. Critically, the addition of a massless, rigid, convex contact head to a multi-degree of freedom (MDOF) pantograph defines a surface which allows accurate contact interaction with the current wire, with the latter consisting of beam elements. A series of high-speed dynamics simulations on multispan catenaries are conducted, comparing well with known benchmarks and EN50318:2018 + A1:2022. Investigation of a two-pantograph system reveals that a trailing pantograph experiences more widely separated contact force extrema than the leading pantograph. The proposed model can easily handle simultaneous contact of the pantograph with multiple wires in overlap sections. Parametric studies reveal that the model’s predictions are robust to small changes in the uplift force and material properties. Finally, friction has only a slight effect on the filtered contact force response.]]></description>
      <pubDate>Tue, 28 Oct 2025 13:46:42 GMT</pubDate>
      <guid>https://trid.trb.org/View/2591457</guid>
    </item>
    <item>
      <title>Design of n -Layer Flat Wire Winding in Permanent Magnet Machine for Electric Vehicles</title>
      <link>https://trid.trb.org/View/2559232</link>
      <description><![CDATA[In the traditional 2k -layer ( k=1 , 2, 3,… ) flat wire winding, the number of turns per phase is limited to be even number. It makes the performance pairing between the vehicle and its electric machines difficult, including the dc bus voltage and the torque-speed curve. In this article, the general design method of n-layer ( n=1 , 2, 3,… ) flat wire winding is analyzed for permanent magnet (PM) machines applied in electric vehicles (EVs), including the design of basic connection unit, the elementary branch, and the parallel branch. Apart from the design of even-layer winding, i.e., n=2k , the number of winding layers can also be designed as an odd number, i.e., n=2k−1 , in the proposed design method, which can lower the pairing difficulty between the required torque-speed curve and the dc bus voltage. In addition, compared with the existing even layer design method, the proposed flat wire winding design method can reduce the manufacturing cost by using less flat wire pin types. The proposed design method can support the design of both full pitch winding and short pitch winding. The proposed design method is verified by a finite element (FE) analysis by comparatively analyzing five-, six-, seven-, and eight-layer winding machines having both full and short pitch windings. Both six- and seven-layer full pitch winding PM machine prototypes, which are designed based on the n-layer winding layout, are built and tested to validate the proposed flat wire winding design method.]]></description>
      <pubDate>Tue, 12 Aug 2025 16:21:25 GMT</pubDate>
      <guid>https://trid.trb.org/View/2559232</guid>
    </item>
    <item>
      <title>Estimation of Equivalent Thermal Conductivity for Electric Machine Windings Using Conformal Mapping Method</title>
      <link>https://trid.trb.org/View/2559221</link>
      <description><![CDATA[It is important to predict the temperature distribution in the windings of electric machines, where the thermal model of an equivalent homogeneous material is used to simulate the winding conductors as well as the insulation and impregnation between the conductors. This article presents an analytical method for better estimating the equivalent thermal conductivity of the windings. According to the periodicity and symmetry of the heat flux field in the windings, the windings are segmented into square units, while the equivalent thermal conductivity of the whole windings is replaced with those of square units. Conformal mapping and equivalent transformation are used to reduce the complexity of solving the equivalent thermal conductivity of each square unit. Comparative study shows that the proposed analytical model is more accurate than the commonly used models. The partial stator temperature simulation was done to further verify that the proposed analytical model can be well applied to the actual windings. Experiments were conducted by fabricating and testing various winding samples, and a comparison between the finite volume method (FVM) thermal simulation and experimental tests verifies the accuracy of the proposed model.]]></description>
      <pubDate>Wed, 06 Aug 2025 15:02:39 GMT</pubDate>
      <guid>https://trid.trb.org/View/2559221</guid>
    </item>
    <item>
      <title>AC Copper Loss Analytical Models of High-Power-Density Axial Flux Permanent Magnet Motor With Different Wire Types</title>
      <link>https://trid.trb.org/View/2553619</link>
      <description><![CDATA[Axial flux permanent magnet (AFPM) motor has many advantages such as compact structure and high power density and is suitable for electric vehicles, aerospace, renewable energy, and other fields that require high motor performance and installation space. However, the ac copper loss will affect the power density, torque density, and efficiency of the motor. Therefore, this article presents the analytical models of ac copper loss, which can accurately calculate different wire types and different winding methods. First, the conditions affecting ac copper loss are analyzed by finite element (FE) and analytical models. Second, the ac copper loss of different wire types under different working conditions is compared, and the efficiency difference is analyzed. Then, the armature reaction ac resistance of different wire types of windings is measured by the experimental platform. Finally, two prototypes with a rated power of 55 kW are manufactured, and the windings are made of flat and round copper wire. The prototype efficiency is measured experimentally based on loss separation.]]></description>
      <pubDate>Fri, 18 Jul 2025 15:10:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/2553619</guid>
    </item>
    <item>
      <title>Unequal-Thickness Flat Wire Winding-Based Eddy Current Loss Reduction for Coreless Axial Flux Permanent Magnet Synchronous Machine Adapted to Extended-Range Electric Vehicles</title>
      <link>https://trid.trb.org/View/2553498</link>
      <description><![CDATA[Axial flux machines are increasingly attracting attention due to their power density and compact structure, making them particularly suitable for extended-range electric vehicles (EREVs). Among these, the coreless axial flux permanent magnet synchronous machine (CAFPMSM) with flat wire is renowned for its high copper filling, thermal conductivity, and efficiency. However, the flat wire in CAFPMSM is subject to substantial eddy current losses induced by the magnetic field. To mitigate eddy current loss, an unequal-thickness winding structure with multilayer flat wire is proposed in this article. A mathematical model is first developed to quantify the eddy current losses based on the air-gap flux density distribution. The relationship between the thickness of each layer of the winding and the resulting eddy current loss is analyzed. Second, the proposed winding configuration is further evaluated through 3-D finite element analysis (FEA) to assess its effectiveness in reducing losses. Finally, comprehensive experiments are carried out to demonstrate the effectiveness of the unequal-thickness windings in reducing eddy current loss and improving the efficiency of the machine.]]></description>
      <pubDate>Wed, 18 Jun 2025 14:41:35 GMT</pubDate>
      <guid>https://trid.trb.org/View/2553498</guid>
    </item>
    <item>
      <title>A Co-Planar Transformer With Ultralow Parasitic Capacitance for EV Chargers</title>
      <link>https://trid.trb.org/View/2512104</link>
      <description><![CDATA[The rising popularity of planar transformers (PTs) in isolated power converters for applications such as electrified transportation and electric vehicle (EV) chargers is driven by their compact design, high power density, and precise manufacturing. However, traditional PTs suffer from elevated interwinding and intrawinding capacitances due to the extensive surface overlap in their flat winding structure. This high parasitic capacitance can lead to voltage overshoot, ringing, and reduced noise immunity, impacting the converter’s regulation capability. To address these challenges and optimize PT performance for higher frequencies, a new co-PT (CPT) is introduced. The CPT minimizes surface overlap by siting the primary and secondary windings on the same plane, leveraging an ultraflat conductor thickness. This design reduces both inter- and intrawinding capacitances without compromising winding area or interleaving of layers. This article explains the proposed CPT structure and presents design examples to illustrate its effectiveness. Three types of PTs from existing literature are used for benchmarking and comparison with the proposed CPT. Impedance measurements reveal a substantial reduction in winding capacitance through the proposed CPT, reaching approximately 18 times lower stray capacitance. Experimental testing with a 5-kW isolated dual-active bridge (DAB) converter demonstrates that the proposed CPT outperforms other configurations in terms of power efficiency, ringing noise, and voltage overshoot. Importantly, the enhanced performance is achieved without increasing build material costs.]]></description>
      <pubDate>Thu, 05 Jun 2025 13:59:26 GMT</pubDate>
      <guid>https://trid.trb.org/View/2512104</guid>
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