Litz-wire high-frequency gapped-transformer (Lw-HFGT) is a vital component that facilitates efficient operation of LLC converters. The converter designers go through cumbersome multiobjective optimization techniques, with many iterations, to obtain an optimal Lw-HFGT design. High reliance on such techniques is due to deficiencies in existing analytical core and winding selection (CWS) methodologies; most analytical CWS models do not focus on optimization. Therefore, this article proposes noniterative analytical CWS methodology for Lw-HFGT based on an innovative optimal core-geometry factor model (OKGM). The aim is to obtain Lw-HFGT design with minimized losses and size, integrated magnetizing inductance, and temperature rise within limits. The method incorporates application requirements (excitation-voltage waveform, LLC circuit-parameters, thermal limit), along with Lw-HFGT physical characteristics [core geometrical features, peak flux density $(B_{{\rm{pk}}})$, current density, core-material parameters, air-gap, effective permeability, and Litz-wire-sizing (LwS)] in the CWS process. Analytical models with improved accuracy for core geometrical features extraction from core-geometry factor, optimal-$B_{{\rm{pk}}}$, and LwS are also proposed. The complete methodology is improved based on proposed models, optimality criteria, application requirements, and energy storage inside gapped transformer. Optimal values of initial setup parameters, calculated using optimal-$B_{{\rm{pk}}}$, enable OKGM to carryout optimal CWS in single iteration. The methodology is experimentally validated by designing Lw-HFGT for the 110-kHz, 200-W, 400–12 VDC LLC converter. The PC40-material-based Lw-HFGT design achieves up to 67% reduction in volume-loss product, in comparison to various existing methods with the same input.

中文翻译：

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基于最优磁芯几何因子模型 (OKGM) 的 LLC 转换器利兹线高频间隙变压器 (Lw-HFGT) 的非迭代设计

利兹线高频间隙变压器 (Lw-HFGT) 是促进 LLC 转换器高效运行的重要组件。转换器设计人员通过繁琐的多目标优化技术和多次迭代，以获得最佳的 Lw-HFGT 设计。对此类技术的高度依赖是由于现有分析铁芯和绕组选择 (CWS) 方法的缺陷；大多数分析 CWS 模型并不关注优化。因此，本文基于创新的最优核心几何因子模型（OKGM）提出了用于 Lw-HFGT 的非迭代分析 CWS 方法。目的是获得具有最小损耗和尺寸、集成磁化电感和在限制范围内的温升的 Lw-HFGT 设计。该方法结合了应用要求（激励电压波形、LLC 电路参数、$(B_{{\rm{pk}}})$CWS 工艺中的电流密度、芯材参数、气隙、有效磁导率和利兹线尺寸 (LwS)]。从核心几何因子中提取核心几何特征的精度提高的分析模型，最优-$B_{{\rm{pk}}}$, 和 LwS 也被提出。根据提议的模型、优化标准、应用要求和间隙变压器内部的能量存储，改进了完整的方法。初始设置参数的最佳值，使用优化计算$B_{{\rm{pk}}}$，使 OKGM 能够在单次迭代中执行最优 CWS。通过为 110-kHz、200-W、400-12 VDC LLC 转换器设计 Lw-HFGT，对该方法进行了实验验证。与具有相同输入的各种现有方法相比，基于 PC40 材料的 Lw-HFGT 设计可将体积损失乘积减少多达 67%。