AIBRIEF
Siemens and Reinhausen, the German power transformer equipment maker, are jointly building a solid state transformer — a compact, semiconductor based alternative to traditional iron core transformers — that delivers 800 V DC straight to GPU racks,
A 1-megawatt AI rack on legacy 400-volt AC would need busbars thicker than a forearm. That is the physical constraint now forcing a voltage shift at the rack, and it is the problem Siemens and Reinhausen are trying to solve.
The two companies are jointly developing a solid-state transformer (SST) that delivers 800 volts of DC power directly from medium-voltage grid input to AI datacenter racks, according to industry coverage. Reinhausen, a German engineering firm best known for on-load tap-changers in traditional power transformers, is pairing with Siemens Smart Infrastructure to replace iron-core conversion with semiconductor-based high-frequency switching. The result collapses multiple AC-to-DC stages and produces a DC bus that matches Nvidia's 800 V HVDC rack direction.
The mechanism is convergence: GPU vendors at the load end and power-electronics vendors at the grid end are arriving at the same 800 V standard. Legacy 400 V AC cannot physically scale beyond roughly 600 kW per rack because copper cross-section becomes unworkable. An SST cuts mass, removes conversion stages, and natively outputs the DC voltage GPU racks need.
The caveat: medium-voltage SSTs are unproven at volume, and cost per kilowatt still exceeds legacy iron-core units. The Siemens/Reinhausen play is the first major European grid-edge instance of the voltage shift; whether the economics follow is the open question.