Observed inefficiencies are due to which of the following factors?
- Inefficient Information Technology (IT) device power supplies
- Inefficient transformer-based power distribution units (PDUs)
- Inefficient UPS systems
- Operation at loads well below the design rating of the system
- All of the above
According to the Lawrence Berkeley National Laboratory report, High Performance Buildings: Data Centers Server Power Supplies, the efficiency of server PSUs in past generations, was approximately ______________________
- 100% at 50% load
- 75% at 50% load
- 50% at 50% load
- 25% at 50% load
In high density installations, there is a need for uninterruptible air conditioner fans. Which of the following statements regarding these fans is NOT true?
- During a power failure the air conditioner fans cannot wait for a generator to start and must be supplied with uninterrupted power.
- This is a simple wiring option for either an AC or a DC system.
- ASHRAE and various other organizations have demonstrated the need for uninterruptible operations of air conditioner fans.
- For a DC system this means that air conditioner fans compatible with external DC power must be used - These devices, if even available, are expected to be costly.
Since some currently available AC UPSs are achieving peak efficiencies of 94%, this means the maximum theoretical efficiency advantage for DC power supplies is 6%.
- 6%
- 8%
- 10%
- 12%
Exclusive of cooling systems, many data centers operate at 30% or less efficiency.
- T
- F
The elimination of power distribution unit (PDU) transformers is one of the reasons __________________ has been proposed.
- AC power distribution
- DC power distribution
- Distributed power system architecture
- The central power supply unit
The wiring between the AC UPS or DC plant and the IT loads produces an electrical loss. The losses depend on which of the following factors?
- The operating current
- The size of the wiring
- The length of wire
- All of the above
The cost of a DC UPS system is typically lower than an AC UPS system by 10% to 20%. Which of the following, associated with DC offset this savings?
- Additional engineering
- Specialized breakers
- Wiring distribution costs
- All of the above
Many data centers operating today waste of as much as 10% power. Newer AC approaches exist that achieve virtually the same efficiency gains as can be gained through conversion to DC.
- T
- F
North American data center power distribution efficiencies are lower than the rest of the world due to the historic use of transformer-based power distribution units (PDUs).
- T
- F
A Comparison of AC and DC Power Distribution in the Data Center Outline
The quest for improved efficiency of data centers has encouraged a climate of innovation in data
center power and cooling technologies. In the early 1990s, manufacturers and engineers have suggested a conversion of the data center power architecture to DC from the existing AC. Despite
a predicted a widespread adoption of a DC standard for data center power and evidence that a change to DC distribution is advantageous, the usage of DC relative to AC has declined.
Recently, new proposals have been made based on high voltage DC distribution. These methods overcome some of the earlier problems with DC power. However, The latest high efficiency AC and DC power distribution architectures are shown to have virtually the same efficiency, suggesting that a move to a DC-based architecture is unwarranted on the basis of efficiency.
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| Summary of A Comparison of AC and DC Power Distribution in the Data Center |
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