The Modern Solid-State Transformer Patent Landscape: Eaton
- The 1968 William McMurray SST patent at General Electric expired mid-1980s under the 17-year US term; the foundational SST architecture has been public-domain for four decades.
- Eaton completed its acquisition of Resilient Power Systems on August 6, 2025 for $86 million ($55M cash plus $31M estimated contingent consideration), absorbing Resilient's multi-port medium-voltage SST patent family.
- Eaton's most recent Resilient-line patent, US 12,500,415 ('Solid-state transformer for mitigation of common mode insults'), exemplifies the tightly scoped post-McMurray IP generation.
- ABB and Hitachi Energy together hold the largest single-group SST portfolio (MMC topology, MFT design, grid-interconnect protection), descending from ABB's 2008-2011 PETT traction program.
- Mitsubishi Electric and Toshiba hold the strongest Japanese positions via Shinkansen traction work; startup IP (DG Matrix, Amperesand, Heron, Resilient-via-Eaton) is heavily patent-pending.
The modern solid-state transformer (SST) patent landscape is dominated not by foundational architecture claims but by second- through fourth-generation refinements, and the single most consequential 2025 move was Eaton’s $86 million acquisition of Resilient Power Systems, completed August 6, 2025 (S2). The 1968 William McMurray SST patent at General Electric expired in the mid-1980s under the 17-year US patent term then in effect, placing the core architecture in the public domain for four decades. The IP that actually governs the 2025-2026 commercial SST industry covers specific topology refinements, control algorithms, packaging and thermal-management techniques, fault-handling schemes, and integration with adjacent equipment families.
Eaton Corporation acquired one of the most consequential SST patent portfolios through its acquisition of Austin-based Resilient Power Systems. The $86 million deal comprised $55 million cash paid at closing plus an initial estimate of $31 million in contingent future consideration (S3). The Resilient patent family covers multi-port SST topology, common-mode-insult mitigation circuits, and integration with battery storage. Mike Yelton, president of Eaton’s Americas Region, Electrical Sector, framed the strategic logic: “Resilient’s medium voltage solid-state transformers are a next-generation solution in high-power, direct current (DC) applications in the electric vehicle (EV) market – and there’s huge opportunity for future applications in data centers, port electrification and battery energy storage” (S3). Resilient cofounder and CEO Tom Keister said the combined teams would “support our continued growth in new products and markets, including data centers” (S3). The most recent Resilient grant, US 12,500,415, typifies the post-McMurray generation: narrow engineering improvements to a public-domain core (S4).
ABB Ltd. and Hitachi Energy (the post-2020 separation of ABB’s Power Grids business) collectively hold the largest SST patent portfolio of any single corporate group. The portfolio descends from ABB’s 2008-2011 PETT traction transformer program and includes follow-on work in modular multi-level converter (MMC) topologies, medium-frequency transformer design, and grid-interconnect protection. ABB’s March 2025 strategic equity investment in DG Matrix carried no public IP-licensing component but reads as a cross-licensing positioning move against the multi-port architectures DG Matrix has patented.
Mitsubishi Electric and Toshiba hold the strongest Japanese SST positions, with substantial coverage of traction architectures derived from Shinkansen high-speed-rail work. Siemens, Schneider Electric, GE Vernova, and Alstom each hold significant adjacent IP without the SST-specific concentration of the top three. The startup wave (DG Matrix, Amperesand, Heron Power, Resilient Power-via-Eaton) has filed aggressively, but most filings remain patent-pending.
The freedom-to-operate question is acute for SST startups entering the AI data center segment. The combination of patents at the topology level (ABB, Hitachi, Eaton), the device level (Wolfspeed, Infineon, Mitsubishi), and the system-integration level (NVIDIA’s 800 VDC reference architecture) creates an IP thicket demanding substantial legal due diligence. Whether established suppliers wield their patents to slow startup entry, or take a license-on-reasonable-terms posture to grow the market, will be a defining strategic decision of the 2026-2028 window.
Why It Matters
Eaton’s $86 million acquisition of Resilient Power Systems — $55 million cash at closing plus $31 million in contingent consideration — is the largest completed SST-sector IP transaction as of mid-2025, and it moved one of the most consequential multi-port topology patent families into the hands of an established switchgear manufacturer. For startups entering the AI data center SST market, the IP landscape now combines ABB and Hitachi Energy’s foundational traction-program portfolios, Eaton’s newly acquired Resilient family, and NVIDIA’s 800 VDC reference architecture at the system-integration layer. Whether these incumbents choose to license on reasonable terms or wield patents defensively will be the defining IP question for the 2026-2028 window in which commercial-scale SST deployments are projected to begin.
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](/?p=9044) (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.
