The DC-DC Transition series · Part 17 of 19
The DC-DC Transition · Supplement D

The Solid-State Transformer: Layer 2 supplier dynamics

The solid-state transformer (SST) is the consequential piece of equipment in the 800V DC architecture. And the layer where vendor power is most concentrated in the six-layer stack. Four Western vendors (Eaton, Schneider, ABB, Hitachi Energy) plus three credible Chinese entrants (CRRC, BYD, TBEA) constitute the entire universe. Silicon carbide device concentration + engineering difficulty + capital intensity keep the field narrow. This supplement covers supplier dynamics, competitive positioning at each voltage class, and the strategic implications for operator procurement.

The DC-DC Transition · six supplements
  1. A. The Transition Tax
  2. B. Hybrid Forever
  3. C. The Voltage Ceiling
  4. D. The Solid-State Transformer (you are here)
  5. E. The Sidecar Power Rack
  6. F. The Connector Wars

Companion to the 13-essay main seriesStart with The Architecture Map.

Reader takeaways
SST vendor universe
Western: Eaton, Schneider, ABB, Hitachi Energy (Siemens later). Chinese: CRRC, BYD, TBEA. Total ~7 credible global suppliers.
Concentration
Top 3 Western vendors: ~70% of Western-served AI DC design wins. Chinese: dominant in domestic + Southeast Asian markets.
Pricing power
SST pricing 2024-2026 held firm despite volume growth. Concentration + engineering barriers protect margins vs commoditising LV transformer market.
Design win dynamics
Hyperscaler-scale deals often multi-vendor for supply security; mid-cap operators single-vendor for engineering efficiency.
Lead times
12-24 months for large-scale units (2-5 MW). Chinese-domestic supply 8-15 months. Export controls + CFIUS scrutiny reduce global Chinese availability.
Innovation trajectory
800V products mature. 1500V products in early production 2026-2028. MVDC in R&D + specific utility deployments; Chinese vendors ahead.

01What SST does that legacy transformers do not

A conventional transformer performs one function: voltage step-down from MV AC to LV AC, at a fixed turns-ratio, with electrical isolation. It does nothing else. Downstream from a conventional transformer, additional equipment is required to rectify AC to DC (if DC is the ultimate distribution). This adds equipment stages, equipment losses, and specific reliability failure modes.

Figure D.1
Solid-state transformer power flow. From MV AC to DC bus
MV AC input13.8-33 kVSST high-voltage stageRectify + isolateDC-DC conversionRegulate to 800V or 1500V DCDC output800V or 1500V DC busBuilding distributionLayer 3 downstream
SST performs three functions traditional transformer does not: (1) voltage rectification + isolation in one stage, (2) intermediate DC-DC conversion, (3) output regulation to specific DC voltage. Enables direct MV-to-DC without intermediate LV AC stage.

An SST integrates rectification + voltage regulation + isolation in a single equipment stage using silicon carbide power electronics. Directly converts MV AC input to specified DC output voltage. Voltage regulation is active (not fixed-ratio like conventional transformer). Fault interruption is inherent in the power-electronic stage rather than requiring downstream mechanical breakers. End-to-end efficiency 2-4 percentage points above LV transformer + rectifier stack.

02Vendor landscape and concentration

Figure D.2
SST vendor landscape: Western + Chinese by product readiness
800V product1500V roadmapMVDC R&DAI DC design winsGlobal availabilityEatonYes2027YesMultipleGlobalSchneider ElectricYes2026-27YesMultipleGlobalABBYes2027YesGrowingGlobalHitachi EnergyYes2028YesUtility-adjGlobalSiemensLater2028+YesLimitedGlobalCRRC (CN)YesAvailableYesCN domesticCN+SEABYD (CN)YesAvailableR&DCN domesticCN+SEATBEA (CN)YesAvailableYesCN domesticCNIntensitylow → high
Western vendors mature at 800V DC + emerging 1500V DC. Chinese vendors ahead on MVDC + broader voltage-class availability, driven by domestic AI infrastructure demand + industrial policy support. Global availability constrained by CFIUS + export controls (see Regulatory VII).

Chart 1. Western vs Chinese SST vendor market share 2026 (est)

Western vendors dominate outside China: Eaton ~22%, Schneider ~18%, ABB ~16%, Hitachi Energy ~12%, Siemens ~5%. Chinese vendors dominate domestic + SEA: CRRC ~40%, BYD ~25%, TBEA ~15%. Global shares differ materially by geography.

03Why the field stays concentrated

Figure D.3
SST value proposition vs execution difficulty
SST advantageWhy AI DC operators want SSTDirect MV to DC in one equipment stageHigher end-to-end efficiency (2-4 pp above LV transformer stack)Voltage regulation + rectification integratedFault interruption faster than mechanical breakersEnables 1500V DC + higher without step-changeSST challengeWhat makes SST hardSilicon carbide devices at MV expensiveThermal management at high current densityInsulation coordination at MV DCLong lead times (12-24 mo for large units)Vendor concentration limits pricing pressure
SST offers material advantages over LV transformer stack but engineering + supply-chain challenges are real. Western vendor concentration (4-5 credible) means pricing pressure limited; Chinese entry increases global competitive intensity but export access constrained.

Chart 2. SST manufacturing capex + engineering entry barrier

Entering credible large-SST manufacturing requires: ~$300-800M facility investment, 5-8 years engineering + design certification, specific SiC device supply relationships (Wolfspeed, ST, onsemi), test + validation infrastructure. Total 8-12 year investment horizon deters new entrants.

04Chinese vendor competitive dynamics

CRRC + BYD + TBEA benefit from three specific advantages: (1) domestic scale from Chinese AI infrastructure buildout provides amortisation base, (2) industrial-policy support keeps capital costs low, (3) SiC device supply from Chinese domestic sources (Sanan, TianKe) reduces cost + supply constraint vs Western supply chain. Global export access constrained by CFIUS scrutiny + specific export-control considerations, but Chinese domestic + Southeast Asian + Middle East + African markets substantial + growing.

Chart 3. Chinese SST vendor capacity + geographic access 2026

Chinese vendors have ~40 GW aggregate annual manufacturing capacity (2026), growing to ~80 GW by 2028. Geographic access: dominant China + growing SEA + material Middle East + emerging Africa. Restricted from most Western markets by regulatory + national-security considerations.

05Operator procurement implications

For hyperscaler-scale deployments: dual-source procurement (typically Western + Chinese where geographically permissible; two Western vendors otherwise) for supply security. For mid-cap operators: single-vendor typical for engineering efficiency + volume pricing. For AI-native GPU cloud operators: often single-vendor determined by contract-collateralised financing lender preferences (see Fin I DDTL).

Chart 4. Operator procurement patterns by scale + type

Hyperscaler: dual-vendor or triple-vendor. Mid-cap operator: single-vendor with contingency. AI-native GPU cloud: single-vendor lender-preferred. Traditional colo: single or dual depending on refresh cadence. Patterns reflect scale + engineering resource + capital-structure constraints.

Method and sources. Public information only. Vendor product datasheets + investor commentary 2024-2026. Yole Group + OMDIA power-electronics market analyses. Industry reporting on SST design wins + capacity.

Series footer. Supplement D to The DC-DC TransitionRelated: Supplement C (voltage ceiling context), DC-DC XI (vendor economics), AI Power ChainHub: AI Power Semi hub.

The DC-DC Transition: start with the foundation
  1. The real reason data centres are going DC (four forces)
  2. Two architectures wearing the same name (800V DC vs OCP Mt Diablo)
  3. The six-layer architecture map