Ferrites and Nanocrystalline Alloys Applied to DC–DC Converters for Renewable Energies

Abstract

The medium frequency transformer (MFT) with nanocrystalline alloys is quintessential in new DC–DC converters involved in various front-end applications. The center piece to achieve high-performance, efficient MFTs is the core. There are various options of core materials; however, no deep information is available about which material characteristics and design procedure combo are best to get high performance MFTs while operating at maximal power density. To provide new insights about interrelation between the selection of the core material with the compliance technical specifications, differently to other proposals, this research work aims to design and build, with the same methodology, two MFT prototypes at 20 kHz, with nanocrystalline and ferrite cores, to highlight power density, and overall performance and cost, as matching design criteria. As the experimental results show, a nanocrystalline core has the highest power density (36.91 kW/L), designed at 0.8 T to obtain low losses at 20 kHz, achieving an efficiency of 99.7%. The power density in the ferrite MFT is 56.4% lower than in the nanocrystalline MFT. However, regarding construction cost, the ferrite MFT is 46% lower, providing this a trend towards low-cost DC–DC converters. Finally, high power density in MFTs increases the power density of power DC–DC converters, which have relevant applications in fuel cell-supplied systems, renewable energies, electric vehicles, and solid-state transformers.

High-Power-Factor LC Series Resonant Converter Operating Off-Resonance with Inductors Elaborated with a Composed Material of Resin/Iron Powder

“…Equation ( 16) is integrated to find the average power From Equation (17), it is possible to obtain the averag ered by the rectifier, which is defined as Equation ( 16) is integrated to find the average power in a high-frequency cycle:…”

“…From Equation (17), it is possible to obtain the average high-frequency current delivered by the rectifier, which is defined as…”

“…The problem with using ferrite cores is that they have a low saturation flux density, typically between 0.2 and 0.5 T, whereas air-core inductors have drawbacks with unwanted stray inductances, causing electromagnetic interference that can affect nearby devices [14][15][16]. Regarding the nanocrystalline cores, these belong to the category of the so-called "soft magnetic composites", which have presented good magnetic properties such as high saturation flux density, high permeability, and a high Curie temperature, in addition to being more resistant in structure compared to ferrite cores [17,18].…”

“…Electronics 2022, 11, x FOR PEER REVIEW 2 of 18 affect nearby devices [14][15][16]. Regarding the nanocrystalline cores, these belong to the category of the so-called "soft magnetic composites", which have presented good magnetic properties such as high saturation flux density, high permeability, and a high Curie temperature, in addition to being more resistant in structure compared to ferrite cores [17,18]. The problem with these nanocrystalline cores is their high cost, which causes the converter to raise its total price and does not comply with the economic saving desired by consumers [11,19].…”

Design of High-Power Solid-State Transformers with Grain-Oriented Electrical Steel Cores

“…They are also more expensive than ferrites. Papers [34][35][36] propose three key elements: a method helping to choose the best magnetic material; they propose a design and an implementation of a high-power high-frequency transformer and cooling pipes around the core in order to reduce the hot spots.…”