Marek S. Rylko

CCTT-Core Split-Winding Integrated Magnetic for High-Power DC–DC Converters

A novel CCTT-core split-winding integrated magnetic (IM) structure is presented in this paper. The IM device is optimized for use in high-power dc–dc converters. The IM structure uses a split-winding configuration which allows for the reduction of external leakage inductance, which is a problem for many IM designs. Magnetic poles are incorporated to help shape and contain the leakage flux within the core window. Low-cost and low-power loss ferrite is used which results in a very efficient design. An IM reluctance model is developed which uses fringing equations to develop a more accurate design. An IM design algorithm is developed and implemented in Mathematica for design and optimization. FEA and experimental results from a 72 kW, (155-V dc, 465-A dc input, and 420-V dc output) prototype validate the new IM concept. The 72 kW CCTT- core IM was shown to be 99.7% efficient at full load.

Magnetic Material Selection for High Power High Frequency Inductors in DC-DC Converters

Dc-dc converter size and efficiency are driving factors in industrial, aerospace and automotive applications. Thus, optimal component selection is essential for a compact design. The inductor often appears as the converters largest component. This paper presents analytical and experimental comparisons of the magnetic materials used in a practical design. The investigation is concerned with magnetic material selection for a dc-dc power inductor in the medium (20 kHz) to high (150 kHz) frequency range and the low (1%) to high (220%) current ripple range. The materials under investigation are iron-based amorphous metal, silicon steel, nanocrystalline, ferrite, powdered iron and gap-less powder materials. A newly developed silicon steel material from JFE-Steel Co. is presented. A novel material comparison which includes thermal conductivity and saturation capability is proposed. The area product analysis for material comparison is presented for 10 kW dc-dc inductor design examples. The variation of core power loss with dc-bias is experimentally investigated for different materials. A 1.25 kW half-bridge dc-dc converter is used in experimental validation.

Revised Magnetics Performance Factors and Experimental Comparison of High-Flux Materials for High-Current DC–DC Inductors

High-flux-density materials, such as iron-based amorphous metal and 6.5% silicon steel for gapped inductors, and powdered alloys for gapless inductors, are very competitive for high-power-density inductors. The high-flux-density materials lead to low weight/volume solutions for high-power dc-dc converters used in hybrid-electric and electric vehicles. In this paper, the analytical selection of the magnetic materials is investigated, and modified performance factors are introduced for convection- and conduction-cooled magnetic components. The practical effects of frequency, dc bias, flux-density derating, duty cycle, airgap fringing on the core loss, and thermal configuration based on lamination direction are investigated for iron-based amorphous metal, 6.5% silicon steel, and iron-based powdered alloy material. A 2.5-kW converter is built to verify the optimum material selection and thermal configuration. Analytical, simulation, and experimental results are presented.

Novel CCTT-core split-winding integrated magnetic for High-Power DC-DC converters

A novel CCTT-core split-winding integrated magnetic (IM) structure is presented in this paper. The IM device is optimized for use in high-power dc-dc converters. The IM structure uses a split-winding configuration which allows for the reduction of external leakage inductance, which is a problem for many IM designs. Magnetic poles are incorporated to help shape and contain the leakage flux within the core window. Low cost and low power loss ferrite is used which results in a very efficient design. An IM design algorithm is developed and implemented in Mathematica for design and optimization. FEA and experimental results from a 80 kW prototype validates the new IM concept and the CCTT magnetic was shown to be 99.7% efficient at full load.

CCM and DCM Operation of the Interleaved Two-Phase Boost Converter With Discrete and Coupled Inductors

Coupled-inductor interleaved boost converters are under development for high-current, high-power applications ranging from automotive to distributed generation. The operating modes of these coupled-inductor converters can be complex. This paper presents an investigation of the various continuous-current (CCM) and discontinuous-current (DCM) modes of operation of the coupled-inductor interleaved two-phase boost converter. The various CCM and DCM of the converter are identified together with their submodes of operation. The standard discrete-inductor interleaved two-phase boost can be seen as a subset of the coupled-inductor converter family with zero mutual coupling between the phases. The steady-state operating characteristics, equations and waveforms for the many CCM and DCM will be presented for the converter family. Mode maps will be developed to map the converter operation across the modes over the operating range. Experimental validation is presented from a 3.6 kW laboratory prototype. Design considerations and experimental results are presented for a 72 kW prototype.

A comparison of classical two phase (2L) and transformer — Coupled (XL) interleaved boost converters for fuel cell applications

This paper investigates power interfaces for a PEM fuel cell. The main focus of the investigation is to analyze and test the effects of part-load operation on component selection and stresses with an emphasis on the magnetic components. The standard two-phase interleaved boost with a discrete inductor per phase is compared with the transformer-coupled two-phase interleaved boost, consisting of a single input inductor in series with a phase-coupling transformer. The converter characteristics are investigated for the experimental V-I inputs derived from the polarization curve of an industrial PEM fuel cell. Experimental validation is presented for a 3 kW design. Magnetic sizing of air-cooled components for power converters up to 45 kW are additionally investigated.

Comparison of 8-kW CCTT IM and Discrete Inductor Interleaved Boost Converter for Renewable Energy Applications

This paper presents a comparison of two magnetic component topologies for use in a high-power high-current dc-dc boost preregulator for renewable applications. The industry-standard two-phase (2L) interleaved dc-dc boost converter consisting of two discrete toroid magnetic components is considered as the baseline design. A 3C92 CCTT-core split-winding integrated magnetic (CCTT IM) is developed and compared for similar conditions. The topologies are compared for the same worst case phase-current ripple conditions. First, the baseline industry-standard 2L design is presented, which consists of a toroidal magnetic component along with stranded copper conductors, which are used to reduce the effects of ac copper loss. The CCTT IM component is designed for the same worst case phase-current ripple as this allows for a size saving with respect to the baseline design. The CCTT IM boxed volume is investigated as the number of turns is varied, but for a like-for-like comparison, the final CCTT IM design has the same number of turns and copper cross-sectional area as the 2L baseline design. A 2D finite element analysis (FEA) is used in order to validate and optimize the designs. The 8-kW experimental results are presented that indicate that the CCTT IM option allows for an approximate reduction of 50% in both magnetic mass and boxed volume with respect to the 2L toroid inductors. Critically, this size saving does not come at the expense of reduced efficiency, and the CCTT IM exhibits greater efficiency than the 2L baseline design. The IM does require additional input capacitance compared to the 2L design. The overall

Magnetic material comparisons for high-current gapped and gapless foil wound inductors in high frequency dc-dc converters

LC

Comparison of CCTT-core split-winding integrated magnetic and discrete inductors for high-power DC-DC converters

filter of the IM design, comprising the boost magnetics and input capacitance, is reduced by approximately 20% in volume and 44% in mass compared to the 2L design.

Experimental investigation of high-flux density magnetic materials for high-current inductors in hybrid-electric vehicle DC-DC converters

The inductor often drives the dc-dc converter size. Thus, the inductor optimization process is required for the most effective design. The paper presents inductor analysis only. The material properties are essential for the design size. In this paper, various magnetic materials are analysed and investigated for use in a practical design. The investigation is concerned with the magnetic material selection for a dc-dc power inductor in the medium (20 kHz) to high (150 kHz) frequency range. The materials under investigation are iron-based amorphous metal, silicon steel, nanocrystalline, ferrite, and gap-less powder materials. A lumped parameter algorithm is derived which includes such effects as the foil ac copper loss effects, the gap core loss, and the cooling path. The algorithm is implemented in EXCEL and generates material comparisons over a range of frequencies, ripple ratios, cooling paths. The results show that the core power loss limited inductor tends to be oversized while the minimum size is achieved for the design which is at the sweet-spot where the size is driven by the core power loss, winding power loss and core saturation limit. A 1.25 kW half-bridge dc-dc converter is built in order to proof the algorithm feasibility at the interest frequency range.