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Siemens and Reinhausen build 800 VDC transformer for AI racks

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Siemens and Reinhausen build 800 VDC transformer for AI racks

Siemens and fellow German engineering firm Reinhausen are developing a solid-state transformer (SST) designed to deliver 800-volt DC power directly to increasingly dense AI datacenter racks. The modular unit converts medium-voltage AC at up to 36 kV into a stable 800 VDC output for downstream distribution. Siemens says the SST offers a compact, galvanically isolated alternative to conventional multistage AC-to-DC conversion architectures, cutting the number of intermediate conversion stages and enabling more efficient power delivery to high-density AI infrastructure. Reinhausen frames the problem in terms of reliability: datacenters running AI workloads are among the industry's most demanding power consumers, and sudden load spikes can strain servers, storage and cooling systems, reducing performance or causing outages. "Our technology enables AI datacenters to operate with the efficiency and reliability they require," said Reinhausen managing director Wilfried Breuer. Siemens CEO of Electrification and Automation Stephan May added that solid-state transformers are critical for large, power-intensive facilities because they enable higher efficiency, direct grid-to-rack DC conversion and a reduced footprint. The push toward 800 VDC follows a direction Nvidia has been advocating: as The Register reported previously, Nvidia sees 800 VDC distribution as necessary once IT racks draw 1 MW or more, a figure that looks aggressive next to today's industry-average rack density of just over 11 kW, per the Uptime Institute, but hyperscalers including Google are already planning for megawatt-scale racks. Nvidia has developed its own MGX-compatible 800 VDC power rack, due to arrive in the second half of 2026. Siemens and Reinhausen said they intend to industrialize their datacenter SST but did not disclose a commercial availability date. A third German electrical firm, Infineon, is also backing 800 VDC and positioning its silicon carbide power semiconductors for use in that infrastructure.

Key facts

  • Siemens and Reinhausen are developing a modular solid-state transformer that converts medium-voltage AC at up to 36 kV into a stable 800 VDC output for AI datacenter racks.
  • Nvidia says the shift to 800 VDC distribution will be necessary once IT racks draw 1 MW or more, versus today's industry-average rack density of just over 11 kW (Uptime Institute).
  • Nvidia's own MGX-compatible 800 VDC power rack is due in the second half of 2026.
  • Siemens and Reinhausen intend to industrialize their SST but have not disclosed when it will be commercially available.
  • German chipmaker Infineon is separately backing 800 VDC with silicon carbide power semiconductors for the same infrastructure.

Why it matters

AI hardware's power draw is outrunning the electrical architecture most datacenters were built around. Conventional multistage AC-to-DC conversion adds inefficiency and bulk at exactly the moment racks need more power delivered more densely. An 800 VDC solid-state transformer collapses that conversion chain into a single, more efficient, smaller-footprint step, which is why two established German electrical engineering firms are jointly building one rather than leaving the problem to chipmakers alone.

Who it affects

Datacenter operators and hyperscalers planning next-generation AI infrastructure, since 800 VDC changes how power is distributed from the grid down to the rack. It also affects the broader electrical-equipment supply chain around AI infrastructure: Siemens and Reinhausen are competing and cooperating in the same space as Nvidia, which has its own 800 VDC rack coming, and Infineon, which is positioning silicon carbide semiconductors for the same shift.

How to use it

There is nothing to deploy yet. Siemens and Reinhausen have said only that they intend to industrialize the SST; no commercial availability date, pricing or power-capacity rating for the unit itself has been disclosed. Operators evaluating 800 VDC today would currently look to Nvidia's MGX-compatible rack, slated for the second half of 2026, rather than this collaboration.

How solid is it

The claims come directly from the companies involved, via named executives (Reinhausen's Wilfried Breuer and Siemens' Stephan May), and the wider 800 VDC push is corroborated by The Register's earlier reporting on Nvidia's stated position and by Uptime Institute's rack-density figures. What is missing is independent verification of the SST's actual performance or timeline, since neither company has published technical specifications for power capacity or a launch date.

Risks and caveats

The gap between the 1 MW rack draw Nvidia says will require 800 VDC and today's roughly 11 kW industry-average rack density is large, and the article itself flags that the projection may sound far-fetched even as it notes hyperscalers like Google are already planning for megawatt-scale racks. No customers, pilots or deployment sites for the Siemens/Reinhausen SST are named, and with no commercial date set, the technology remains a development effort rather than a shipping product.

“Solid-state transformers are critical for these large and power intensive structures. They enable higher efficiency, direct grid-to-rack DC conversion, and a reduced footprint. This collaboration will further strengthen our leading position in the electrification of datacenters.”

— Stephan May, Siemens CEO of Electrification and Automation