Delve into the innovative features of Vertiv™ PowerDirect Rack 33kW and find out how it redefines power delivery for modern data centers.
*This blog is the third of a series identifying the promise of HVDC for data centers, early adoption case studies, and how rack-level DC power systems provide a practical bridge to an HVDC-enabled future.
Modern data centers must manage compounded growing power needs while balancing efficiency, scalability, and environmental goals. As facilities rely on AC utility feeds, operators don’t need to overhaul their entire site to high-voltage DC (HVDC) to increase energy efficiency and maximize usage. Vertiv™ PowerDirect Rack 33kW is at the forefront of this transformation. Compact, modular, and future-ready, this DC power system delivers the flexibility and performance required for today’s AI and hyperscale workloads.
Efficiency key: Reducing the AC-DC conversion steps
To understand the comparison of traditional AC power architectures and how DC-powered facilities are more efficient, read the first blog of this series, “Bridging the Present to the Future: Rack-level DC Power Distribution for Legacy AC Designs”
The reduction in the number of conversion steps stems from the elimination of the uninterruptible power supply (UPS) and the use of battery backup units (BBUs) on the 50VDC rail. For very high-powered racks, the BBUs take up too much rack space and the UPS is still used. Therefore, there is no reduction in the number of conversion steps.
The efficiency improvement is due to the AC to 50VDC bulk power supplies being more efficient than the embedded power supplies housed in the server. Furthermore, most of the embedded power supplies are operating at less than half of their output rating due to each one being paired with a redundant unit. The 50VDC units are all operating in parallel; a quantity can be deployed to maximize efficiency while maintaining redundancy. Also, moving the power conversion out of the server frees up space within the server for more computing components and simplifies the server design. This is especially significant in AI and HPC environments, where maximizing compute density per rack is critical. Freeing up internal space allows for more GPUs, memory, or accelerators, driving higher performance in the same footprint while reducing complexity and improving airflow for better thermal management.
Figure 1. Architecture 2: Rack power with central UPS (top) and Architecture 3: Rack power with in-rack battery backups (BBU) (bottom)
| Data center power architecture evolution: Migrating power protection from room to rack | |
| Architecture 2: Rack power with central UPS | Architecture 3: Rack power with in-rack battery backups (BBU) |
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Table 1. From Architecture 1, making energy supply and distribution more efficient by reducing the conversion steps.
HVDC eliminates some conversion steps. For example, with UPS and 50VDC power systems, there are four conversion steps to get to the server, whereas the use of HVDC systems in place of the UPS reduces the number of steps to two conversions: AC to DC in the HVDC output system and DC to DC in the 50VDC output system.
Efficiency at work: Vertiv™ PowerDirect Rack 33kW
To illustrate how rack-level DC power works in the real world, Vertiv™ PowerDirect Rack 33kW can be used as an example. Vertiv™ PowerDirect Rack is a DC power shelf solution engineered for modern data centers, bringing a resilient, scalable power backbone right into the IT rack, with features that align to hyperscale and AI data hall needs.
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Figure 2. The Vertiv™ PowerDirect In-Rack 33kW 50V DC Power System is a high-density, scalable DC power system designed for modern data centers and Open Compute ORV3 environments. Ideal for high-capacity server setups, it maximizes power efficiency and minimizes space requirements.
- High power density: Each Vertiv™ PowerDirect shelf delivers 33kW of power (660A at 50VDC) while occupying just 1U of rack space. With the ability to stack up to 132kW per rack, it supports extremely high-density configurations ideal for AI and HPC environments, optimizing floor space and power delivery.
- Modular, hot-pluggable design: Designed for scalability, the system includes hot-swappable 5.5kW power modules managed by a centralized control unit. Additional shelves can be added on the fly, providing flexibility to grow with IT demands while facilitating continuous power delivery. For hyperscale and cloud operations, this continuous uptime, even as density expands, is crucial.
- Dual AC/HVDC input compatibility: The Vertiv™ PowerDirect In-Rack is dual-input compatible, supporting both traditional AC and emerging HVDC sources. Operators can feed it with standard AC utility or UPS power (it accepts 400/230 to 480/277 V AC, three-phase), and it will rectify that to 50VDC for the IT load. Tomorrow, if the facility adopts a 380VDC bus or other HVDC source, the same Vertiv™ PowerDirect units can accept a DC input (190–410VDC range) natively. In both cases, the output to the servers remains stable at 50VDC. This dual input facilitates long-term adaptability, allowing operators to leverage today’s infrastructure while preparing for the transition to high-voltage DC power.
- Peak efficiency: With conversion efficiency reaching up to 97.5%, the Vertiv™ PowerDirect Rack minimizes power losses while easing cooling requirements. This means almost all the input power is delivered to the servers, with only minimal losses as heat. For data center operators, that translates to lower energy bills and less strain on cooling systems, compared to typical server PSUs or older AC UPS solutions, and is especially important at scales of 100kW per rack. High efficiency at partial loads also translates that facilities are not being **penalized during normal (non-peak) operation. By delivering maximum usable power to servers, Vertiv™ PowerDirect Rack can maximize efficiency across the board. By delivering maximum usable power to servers, Vertiv™ PowerDirect Rack can maximize efficiency across the board.
- Open Compute Project (OCP) compliant and integration-ready: The Vertiv™ PowerDirect Rack supports seamless deployment in modern OCP racks as it is compliant with OCP Open Rack V3 HPR specification standards. This means it can seamlessly fit into modern OCP racks used by hyperscalers. It also uses the standardized form factor and bus bar connections of ORV3 HPR for 48V/50V distribution. However, its benefits are not limited to OCP; any data center looking to deploy 48–50V DC distribution can leverage this solution. Vertiv™ PowerDirect Rack’s flexible design makes it suitable for retrofitting into existing environments (e.g., modular cabinets or custom racks) and greenfield deployments alike.
**“Penalized” in this sense pertains to the indirect accumulated price that facilities pay for the use of higher electricity costs brought by extra cooling and inefficient use of power. This higher energy waste and costs occur when equipment runs at partial (non-peak) loads. Vertiv™ PowerDirect Rack prevents this efficiency drop in facilities.
Taking the leap to power efficiency
DC power architecture enhances efficiency and supports higher power densities per rack compared to traditional systems. It enables operators to scale power while increasing computing demands brought by the rapid AI/HPC use, addressing the limitations of older designs. Additionally, it serves as a practical step toward integrating HVDC systems, offering a bridge between current AC-based facilities and future DC-powered setups.
The Vertiv™ PowerDirect Rack represents a leap forward in power technology, offering business foresight, high power density, and modularity in a single solution. Whether addressing today’s AI-driven workloads or preparing for an HVDC future, Vertiv solutions set a new benchmark for efficiency and scalability in data center power delivery.
