Vacuumschmelze VITROPERM and Hitachi Metals FINEMET: The Two

Two companies dominate the global supply of nanocrystalline magnetic cores used in solid-state transformer (SST) medium-frequency transformers (MFTs). Vacuumschmelze GmbH, headquartered in Hanau, Germany, ships VITROPERM nanocrystalline cores. Hitachi Metals, Ltd. (now part of Proterial, Ltd., spun out of Hitachi Ltd. in 2023), headquartered in Tokyo, Japan, ships FINEMET nanocrystalline cores. Both companies introduced their first commercial nanocrystalline cores in 1992. The duopoly position they hold in the SST industry is one of the most consequential supply-chain constraints in commercial SST production.

The technical advantages of nanocrystalline magnetic materials over conventional silicon steel or ferrite alternatives are substantial. Sub-20-nanometer grain microstructure produces core losses below 10 watts per kilogram at 100 kilohertz operation, approximately one-fifth the core loss of conventional silicon steel at the same operating point. The 1.2 tesla saturation flux density is significantly higher than the 0.3 tesla saturation of competing manganese-zinc ferrite alternatives. The combination of low loss and high saturation enables the compact MFT designs at the heart of every commercial SST.

The market constraint visible in late 2025 and through 2026 is concrete: both VITROPERM and FINEMET production capacity is sold out through mid-2026. The bottleneck is driven not by SST industry demand alone but by the broader $200-billion-plus annual artificial-intelligence capital-expenditure cycle that has elevated demand for high-frequency power-conversion magnetic cores across data center, EV powertrain, and renewable inverter applications simultaneously. SST manufacturers compete for the same nanocrystalline supply as Tier-1 EV powertrain suppliers, the 48-volt-bus converter industry, and the 800-volt DC data center power-shelf market.

The competitive response from Vacuumschmelze and Hitachi Metals/Proterial has been capacity expansion. Vacuumschmelze opened a second VITROPERM production facility in Hanau in 2024. Hitachi Metals/Proterial has announced FINEMET capacity expansion in Japan and is in discussion with multiple international partners for licensed manufacturing in Asia. A third entrant, Beijing-based Advanced Technology & Materials Co. Ltd, has been investing aggressively in nanocrystalline core production through 2024 and 2025, with patent filings in the nanocrystalline alloy space surging above 200 in the 2024-2025 window from a combination of the two incumbents and emerging Chinese competitors.

The strategic question for the commercial SST industry is whether the nanocrystalline-core supply will scale fast enough to support the projected SST manufacturing volumes through 2027 and 2028. Heron Power’s 40-gigawatt-per-year US manufacturing target alone implies several hundred metric tons of nanocrystalline core procurement annually. The combined target across all announced SST product roadmaps approaches 1,000 metric tons per year of nanocrystalline material by 2028, which is several times current global production capacity. The supply chain will either expand aggressively or the SST industry will face material constraints that no other engineering choice can overcome.

Why It Matters

For supply-chain planners, the Vacuumschmelze VITROPERM and Hitachi Metals FINEMET duopoly on nanocrystalline cores is a chokepoint as consequential as SiC wafers, because every SST medium-frequency transformer needs these cores and only two firms have shipped them at scale since 1992. Two suppliers for a mandatory component means SST production ramp is exposed to the same single-source risk that already constrains conventional transformer steel.

Critical Perspective

Editorial correction: This post is part of MGRID’s Solid-State Transformer industry coverage. As of May 2026, that body of work systematically framed manufacturer announcements, funding rounds, and laboratory demonstrations as commercial deployments. The reality is that field-deployed commercial-class SST in revenue service globally is measured in single digits, and almost every product cited in this series is at “announced” or “funded” stage, not “operational.” Readers should treat the specific claims in this post against the standards documented in our SST Industry Reality Check (the per-claim audit table maps marketing language to verifiable deployment status). The corrective article is the canonical reference for SST industry reality; this post remains published with its original framing so the editorial drift is traceable.

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• DG Matrix Ships First Commercially Available Multiport Solid-State Transformer Aligned With NVIDIA 800VDC AI Factory Spec: DG Matrix’s AI factory SSTs use these nanocrystalline cores
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