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How to Build MW Testing Power for AI Server?

The shift from LVDC to HVDC in AI servers brings complex new power testing challenges.
ActionPower's megawatt-class testing solutions are engineered to meet them。

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Power Rating Scales Up as When Server Architecture Upgrades from LVDC to HVDC

HVDC AI Server Reaches 1MW and Here are the Whys and Challenges



The conventional data center relying on a 48V architecture - where power shelves and racks operate at 54 VDC to compensate for voltage drops - is not yet a legacy, but remains a mature option for standard server generations. Within this low-voltage architecture, GPU clusters are supported by power shelves equipped with hot-swappable power modules (handling either AC-DC or DC-DC conversion), with total shelf capacities typically ranging from 15kW to 33kW.

However, as LLM training and real-world workloads scale exponentially, this low-voltage architecture struggles to keep pace. The surging power demand results in an unrealistically high current draw. Delivering such immense power at 54V can generate thousands of amps per rack, thus the required size and weight of copper busbars and cabling are physically and economically impractical.

A schematic diagram of a 415 VAC power distribution system. Power flows from a utility source through a medium voltage network, stepping down to a low voltage main switchboard with diesel generator backup. The 480 VAC power routes through an LVAC UPS and a PDU transformer, stepping down to 415 VAC. It then passes through an AC distribution panel to an AI compute rack, where the PSU converts the 415 VAC to 54 VDC. Optional on-premise generation and energy storage are also depicted.

The advent of HVDC power architecture has thus emerged to resolve the contradiction between the surging server workloads that reach beyond 1MW per rack and the physical limitations of copper busbars and cabling. By converting AC to 800 VDC and routing it directly to the servers, this architecture reduces the number of power conversion stages.

Consequently, data centers avoid the unrealistic hardware costs associated with handling massive 1MW workloads at 48V, while significantly improving overall energy efficiency by minimizing power conversion losses.

A schematic diagram of an 800 VDC power distribution system. Utility, on-premise generator, and BESS sources feed into a medium voltage network. The 13.8 to 35k VAC power is converted by an MV rectifier or solid-state transformer into 800 VDC. This 800 VDC flows through a DC distribution panel, integrates with energy storage, and supplies power directly to a compute rack.

ActionPower's MW-Class High Dynamic Regenerative Test Platform

Challenges for Power Testing Confronting the MW AI Server Workload

Testing the power delivery network for AI servers is not simply about power ratings or dynamics, but rather an interwoven, complex challenge

Programmable power testing for AI server has its focuses around validating whether the power distribution and subsystem can function stable, reliable and resilient against the AI server workload featuring shifting, volatile, unpredictable, and ultra-heavy current draw profile.

Programmable power, or to be more specifically the DC load simulator for such testing applications to replicate the server workload, sees inevitably the below requirements and functional features to achieve and comply with:

High-Dynamics and Fast Response

Replicating volatile power profiles and validating PDN resilience

Real-world AI server workloads exhibit unpredictably volatile power profiles with dramatic shifts in current draw. Consequently, for the electronic DC loads drawing current from the PSU, a high and fast slew rate, defined by di/dt, is a functional imperative. This is crucial for accurately replicating server workloads and validating the resilience of the Power Delivery Network (PDN).

High-Power Replication Capacity

Scaling programmable DC loads via master-slave architecture for MW testing

Even if building a physical 1MW AI rack solely for power testing is theoretically possible, replicating precise GPU workload functions remains a software challenge, and the hardware cost is prohibitive. Programmable DC loads, therefore, must be capable of being parallelled in a master-slave architecture to reach megawatt-level power, all while maintaining minimal accumulated latency and tight synchronization.

Thermal Management & Energy Efficiency

Utilizing regenerative loads to recycle energy and reduce thermal stress

Dissipating megawatt-level power as pure heat overwhelms laboratory cooling capacities and drives up electricity costs exponentially. Therefore, regenerative electronic loads - which recycle over 90% of the absorbed energy back to the grid - are now a strict necessity. To further manage extreme power densities, the testing instruments themselves may even increasingly migrate to liquid-cooled architectures, technically challenging for now though, and most probably in the near future.

PRL DC load simulator by ActionPower. The left side of the picture shows a rack system with 7 units of 5U power unit connected in parallel while the cabinet on the right is one with lower power rating where only 
4 units are paralleled

Regenerative High-Dynamics DC Electronic Load for AI Server Testing

Introduction to ActionPower's PRL DC Load Simulator




Engineered for modern AI data centers, the PRL Series combines ultra-fast linear load dynamics (≤6μs response, up to 60 A/μs slew rate) with regenerative efficiency (recycling up to 87.1% of power to the grid). It is the ultimate testing ecosystem for both 50V/54V compute nodes and 800V/1000V HVDC architectures.

DC Load Simulator PRL

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5U Building Blocks
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Cabinet Scalability
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Inter-Cabinet Parallelation

Scale up from 5U 25kW Modular Chassis

A single 25kW, 5U PRL chassis serves as the foundational building block that delivers the core operating capabilities and technical features required to construct a megawatt-level AI workload simulator.

high power density and overload capability of PRL regenerative load simulator

High-Power Cabinet Build-Up with 7 Units in Parallel

The PRL series features a highly scalable architecture. Up to seven 5U units can be paralleled within a modular cabinet system to deliver 175kW of power from a single platform.

scalability of PRL regenerative load DC simulator

8 Cabinets Master-Slaved for MW Power Scalability

Taking advantage of ActionPower's patented master-slave parallel technology, up to 8 fully loaded cabinets can be connected to build a massive 1.4MW AI server workload simulation platform.

Overview of Parallel Cabinet Setup Options of PRL

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