Kevin J. Hartnett

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.

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.

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

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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.

CCM and DCM operation of the integrated-magnetic interleaved two-phase boost converter

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.

Two-phase interleaved boost converters for distributed generation

This paper presents a comparison of two magnetic component topologies for use in high-power high-current dc-dc boost converters. A 97.2 kW three-phase dc-dc converter prototype is considered as the baseline design. The split-winding integrated magnetic (CCTT IM) and two-phase discrete inductor (2L) topologies are then designed to have the same worst-case phase-current ripple condition for a 72 kW prototype. The magnetic components are optimized for varying number of turns in order to achieve the minimum boxed volume. Magnetic and semiconductor power loss are investigated. High-power experimental results are presented for the baseline 3L (97.2 kW) and CCTT IM (72 kW) converters. 3.8 kW experimental results are presented which compares and validates the 2L and CCTT IM concepts under like-for-like operating conditions.

CCTT-core split-winding integrated magnetic interleaved boost converter for renewable energy applications

Integrated-magnetic interleaved-boost converters are under development for high-current, high-power applications ranging from automotive fuel cells to photovoltaics. This paper presents an investigation of the various continuous-current and discontinuous-current modes of operation of the integrated-magnetic interleaved two-phase boost converter. Experimental validation is presented from a low-power 3.6 kW laboratory prototype.