Nanocrystalline Cores and the Future of High-Frequency Transformer Design
If you've been following transformer material news lately, you've probably noticed that "nanocrystalline" keeps showing up next to "high-frequency." That's not a coincidence. Power electronics designers are pushing switching frequencies well past the old 50 Hz comfort zone, and the materials that worked at grid frequency aren't keeping up.
What Nanocrystalline Actually Is
Nanocrystalline alloys are soft magnetic materials with grain sizes in the nanometer range, produced by rapid solidification of a molten alloy into thin ribbon. The most common commercial composition is iron-based, with additions of copper, niobium, silicon, and boron - the FeCuNbSiB family. Controlled crystallization during annealing produces a microstructure that combines high permeability with low hysteresis loss.
The practical result: a material that behaves differently from both silicon steel and ferrite. It doesn't replace either one across the board, but in the frequency band where ferrite starts to struggle and silicon steel becomes impractical, nanocrystalline sits in a useful middle ground.
Core Loss Comparison: Nanocrystalline vs Ferrite vs Silicon Steel
At 10 kHz, in one study comparing materials for an inductor, the nanocrystalline core showed the lowest loss - the amorphous core had 1.75 times higher loss, and the 6.5% SiFe core had 8.9 times higher loss. At higher frequencies, the gap widens further because silicon steel's eddy current losses scale with frequency squared.
What the Efficiency Numbers Look Like in Practice
A 2026 study in IEEE Transactions on Power Electronics evaluated stress-annealed nanocrystalline (SAN) transformers in 100 kHz dual-active bridge (DAB) converters. Under light load, the SAN-based design delivered efficiency more than 1.4% higher than nanocrystalline flake ribbon and ferrite DMR95, and 2.4% higher than DMR40. Peak efficiency reached 97.2% at a 34.7° phase shift angle. Under specific test conditions, efficiency exceeded 99.1% across the full load range, peaking at 99.6%.
The same study found that SAN transformers kept their efficiency advantage even when volume was cut by one-third or one-half. At 50% volume reduction, SAN transformers still outperformed NFR and ferrite cores, remaining 1.2%–1.6% higher at 0.2 load.
An earlier comparison of 20 kHz DAB converters tells a similar story with more modest numbers:
1.1 kW, 20 kHz DAB converter tests.
The toroidal nanocrystalline transformer delivered roughly 1 percentage point higher efficiency and twice the power density of the ferrite equivalent. If thermal budget and board space are tight, that difference decides the design.
Figure 2. Efficiency and power density by core type in a 1.1 kW, 20 kHz DAB converter. Efficiency shown as midpoint of measured range; full ranges in chart footnote.
Where It Doesn't Work
Nanocrystalline has real constraints, and designers need to account for them.
Eddy current losses rise sharply as frequency climbs. This is the known limitation, and it's the main reason the material's performance advantage narrows at the upper end of the spectrum. For a converter running at 200 kHz or above, that narrowing matters.
Inter-ribbon eddy currents are a second issue. A 2024 study in IEEE Transactions on Magnetics found that electrical isolation among nanocrystalline strips is provided by air gaps, not a true insulating coating like silicon steel sheets. Small contact areas between strips can cause large increments in eddy current losses. Accurate loss modeling for nanocrystalline cores requires more than reading a datasheet - the physical structure of the wound core matters.
The third constraint shows up in gapped designs. For inductors and transformers that need a discrete air gap to avoid saturation, the fringing flux around the gap can cause elevated eddy current losses. Work on gapless designs using nanocrystalline flake ribbon showed that eliminating the gap cut winding losses by 33.2% compared to ferrite and 67.1% compared to conventional nanocrystalline in one 5.5 kW, 100 kHz DAB test.
The Market Context
The global nanocrystalline strips market is expected to reach $1.03 billion by 2032, growing at a 12.6% CAGR from 2026 to 2032. Hitachi Metal leads with roughly 45% share, followed by Advanced Technology and VACUUMSCHMELZE, with the top three holding over 65% combined. China is the largest single market at about 35% share.
Consumer electronics is the largest application segment at roughly 47%, but the growth drivers are shifting toward renewable energy, electric power, and automotive. Photovoltaic inverters moving from 16 kHz to 50 kHz switching, EV onboard chargers, and 5G base station power modules are all pulling demand for materials that ferrite cannot serve at the required flux density.
What This Means for Designers
If your application runs in the tens-to-hundreds of kHz range, and the priorities are efficiency, power density, and thermal performance, nanocrystalline is worth evaluating seriously. The efficiency gains over ferrite are measurable, and the size reduction potential is real.
If your frequency is lower - 50/60 Hz grid applications, for instance - nanocrystalline isn't the answer. Silicon steel or amorphous alloys remain the economically rational choice. Nanocrystalline's cost per kilogram is higher, and the performance advantage that justifies that cost sits in the higher frequency bands.
TIG - Trust in Grid
We manufacture transformers and supply core materials, including nanocrystalline cores for high-frequency applications. If you're working on a converter design and need to evaluate whether nanocrystalline is the right fit, send us your specs - frequency, power level, size constraints, efficiency targets. We'll give you a straight answer.
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References
"Nanocrystalline Cores in High-Frequency DAB Converters: Efficiency and Power Density," IEEE Transactions on Power Electronics, 2026.
"Comparative Core Loss Analysis of Nanocrystalline, Amorphous, and 6.5% SiFe Cores at 10 kHz," IEEE Transactions on Magnetics, 2024.
"Inter-Ribbon Eddy Current Losses in Nanocrystalline Wound Cores," IEEE Transactions on Magnetics, 2024.
"Gapless Nanocrystalline Flake Ribbon Transformers for High-Frequency DAB Converters," IEEE Transactions on Power Electronics, 2025.
"Toroidal vs Cut-Core Nanocrystalline Transformers in 20 kHz DAB Converters," IEEE Transactions on Industrial Electronics, 2024.
QYResearch, "Global Nanocrystalline Strips Market Report 2026–2032."
"Nanocrystalline Alloys: Composition, Microstructure, and Magnetic Properties," Journal of Magnetism and Magnetic Materials, 2023.
Hitachi Metals, "Nanocrystalline Soft Magnetic Alloy Technical Datasheet," 2025.
VACUUMSCHMELZE, "Nanocrystalline Core Loss Data at High Frequency," Technical Note, 2024.
"Photovoltaic Inverter Switching Frequency Trends and Magnetic Material Selection," IEEE Journal of Emerging and Selected Topics in Power Electronics, 2025.