There has been a debate going on for some years if the traditional AC or new DC power distribution is best approach to power a data center. The DC power side has been pushing their technology with claims of quite considerable power savings. In many published articles, expected improvements of 10% to 30% in efficiency have been claimed for DC over AC. I have had my doubts of the numbers on their promises. Now there is some new data on AC vs DC issue available.
White paper compares AC vs. DC power distribution for data centers article tells that a new white paper from APC by Schneider Electric provides a quantitative comparison of high efficiency AC vs. DC power distribution platforms for data centers. The latest high efficiency AC and DC power distribution architectures are shown by the analysis to have virtually the same efficiency, suggesting that a move to a DC-based architecture is unwarranted on the basis of efficiency
A Quantitative Comparison of High Efficiency AC vs. DC Power Distribution for Data Centers paper demonstrates that the best AC power distribution systems today already achieve essentially the same efficiency as hypothetical future DC systems. It also tells that most of the quoted efficiency gains in the popular press are misleading, inaccurate, or false (like I have suspected to be for some time). And unlike virtually all other articles and papers on this subject, this paper includes citations and references for all of the quantitative data (which is very good).
The paper first describes that there are five methods of power distribution that can be realistically used in data centers: two basic types of alternating current (AC) power distribution and three basic types of direct current (DC) power distribution. These five types are explained and analyzed.
One AC and one DC, offer superior electrical efficiency. The paper focuses on comparing only those two highest efficiency distribution methods, which are very likely to become the preferred method for distributing power in future data centers. The data in this paper demonstrates that the best AC power distribution systems today already achieve essentially the same efficiency as hypothetical future DC systems.
The best AC system is based on the existing predominant 400/230 V AC distribution system currently used in virtually all data centers outside of North America and Japan. Increasing Data Center Efficiency by Using Improved High Density Power Distribution white paper gives details how it could be used in USA. It says that the use of the international 230/400 V distribution system instead of the USA standard 120/208 system can save 56% in the lifetime cost of the distribution system, and save floor space and weight loading.
The preferred DC system is based on a conceptual 380 V DC distribution system (consensus in the literature as a preferred standard) supplying IT equipment that has been modified to accept DC power. In the proposed international ETSI standard for DC distribution for data centers, the 380V DC system is actually created with the midpoint at ground potential to keep the maximum system voltage to ground to within +/- 190 V.
Based on the data I think the 400/230 V AC distribution system is the best way to go in data centers around the world.
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Tomi Engdahl says:
What You Need to Know About New Fault-Managed Power Systems
https://www.belden.com/blogs/smart-building/what-you-need-to-know-about-new-fault-managed-power-systems
When the 2023 version of the National Electrical Code (NEC) is released later this year, the industry will be introduced to a new type of power circuit—one that could change the way buildings and technology are powered in the future.
This latest edition of the NEC, set for release in Fall 2022, contains New Article 726, which was created for Class 4 circuits.
The new Class 4 classification standardizes an improved format of electricity. As you hear more about Class 4, you’ll realize it has many names: fault-managed power systems, packet energy transfer (PET), Digital Electricity™ (DE), pulsed power or smart transfer systems. These terms are used interchangeably, but they all refer to Class 4 circuits.
Fault-managed power systems are already in use in some intelligent buildings, but a task group within the NEC recognized that these systems are unique and specialized enough that they need their own code section.
What Are Fault-Managed Power Systems?
To understand Class 4, it’s important to also understand Class 2 and Class 3 circuits.
Class 2 circuits can support lower power (up to 100VA) in many types of environments. They consider safety from a fire initiation standpoint and offer protection from electric shock. Class 2 power loads are often delivered through Power over Ethernet (PoE) cables.
Class 3 circuits function similarly to Class 2 circuits, but they support higher voltage and power limitations. Class 3 power loads can also be delivered through PoE cables.
But while Class 2 and Class 3 systems are power-limited systems with ratings of up to 300 volts, Class 4 is a new standard dedicated to fault-managed power systems with voltage ratings of up to 450 volts.
These fault-managed power systems provide up to 20 times the amount of power or 20 times the distance of PoE and offer a cost-effective alternative to AC power.
What Does “Fault-Managed Power” Mean?
Unlike Class 2 and Class 3 power-limited circuits, Class 4 systems don’t limit power source output.
Instead, they constantly monitor for faults and control the delivery of power current available during an abnormal condition. This mitigates the risk of shock or fire by limiting the amount of energy that can go into a fault.
This technology makes Class 4 systems just as safe as—if not safer than—Class 2 and Class 3 systems. As a result, Class 4 systems can be installed by the same integrators and contractors that also install Category and PoE cabling.
How Do They Work?
Fault-managed power systems can limit available power in a variety of ways.
Let’s use Digital Electricity, created by VoltServer, as a real example. When using Digital Electricity, AC or DC analog electricity comes in from the grid, battery plant or uninterruptible power supply (UPS). A transmitter converts the incoming analog AC or DC power to Digital Electricity.
This Digital Electricity is then split into packetized units that combine power and data so both can be sent via the same structured cable. A receiver converts the Digital Electricity back into analog AC or DC.
Every second, nearly 500 of these packets—each containing a very small amount of energy—move from a transmitter to a receiver.
The steady stream of hundreds of packets per second is continuously monitoring for faults. The transmitter is able to recognize a fault condition within a fraction of a second—improper wiring, short circuit or someone touching transmission lines—and stop packet transmission. This halts the flow of electricity immediately and makes the conductors safe to touch.
In addition to prioritizing safety, Class 4 is also said to be more efficient and cost-effective than the alternatives available to deliver this amount of power across long distances. Because Class 4 uses small conductors, less copper material is required.
Tomi Engdahl says:
Class 4 Fault-Managed Power Systems: An overview of this new classification in the 2023 NEC
https://www.ecmag.com/magazine/articles/article-detail/class-4-fault-managed-power-systems-an-overview-of-this-new-classification-in-the-2023-nec
A Class 4 classification system with Class 4 jacketed cables, dealing with fault-managed power and cabling, has been accepted into the 2023 National Electrical Code as new Article 726.
A Class 4 classification system with Class 4 jacketed cables, dealing with fault-managed power and cabling, has been accepted into the 2023 National Electrical Code as new Article 726.
This new Class 4 system permits safe transfer of higher-voltage power data with load circuits up to 450V peak AC or DC. Either can be used over much longer distances than before.
What’s new in Class 4?
This new system can provide power distribution to power over ethernet, internet of things, smart building systems, monitoring and control of electronics and appliances. It can also be used for control of security systems and electronic components for large areas of a building, stadium or campus.
New Class 4 systems permit larger and more sensitive cameras, more data transfer for cloud backup, and power and data supply for large appliances. These circuits have the capability of taking substantial power, such as 2,000W, over much longer distances.
Class 4 systems appear to be much more usable due to lower voltage drop than older Class 1, Class 2 and Class 3 circuits. These new Class 4 systems, despite the higher voltage and current, are allegedly as safe as the Class 2 and Class 3 circuits.
The active components of a Class 4 circuit must be listed devices, based on 726.170. The listing information includes compatible devices, since a listed Class 4 one depends on specific system devices for interoperability, monitoring or control.
nformational Note 2 provides an example of a dependent active device in a Class 4 system as a transmitter that relies on a particular receiver or receivers as part of the monitoring and control system.
Class 4 transmitters and receivers must be manufactured by the same company, listed together as a system and durably marked with the maximum voltage and current output where plainly visible.
In addition, new 726.1, Informational Note No. 1 states that Class 4 fault-managed power systems consist of a Class 4 power transmitter and a Class 4 receiver connected by Class 4 cabling. These systems (transmitter and receiver) monitor the circuit for faults and control the source current to ensure the energy delivered into any fault is limited.
Class 4 transmitters and receivers must be manufactured by the same company, listed together as a system and durably marked with the maximum voltage and current output where plainly visible.
A Class 4 transmitter must interrupt an energized circuit when any of the following six conditions occur between the transmitter and the receiver: a short circuit; line-to-line fault that presents an unacceptable risk of fire or electric shock; ground-fault condition that presents an unacceptable risk of fire or electric shock; overcurrent condition (of any kind); malfunction of the monitoring or control system that presents an unacceptable risk of fire or electric shock; and any other condition that presents an unacceptable risk of fire or electric shock. Testing and listing the systems should alleviate any concern about them becoming a risk of fire or electric shock.
The outputs of a Class 4 receiver and power outputs of Class 4 utilization equipment are considered a separately derived system if the outputs are used as a supply for a feeder or branch circuit. Article 726 does not reference 250.30 for grounding and bonding requirements for separately derived systems, so assume grounding and bonding based on 250.30 would apply.
Class 4 systems are not permitted to be used for dwelling units, especially due to the required voltage limitations in 210.6 of the NEC. Class 4 cables are special cables covered in new Article 722. Connecting hardware must be listed for Class 4 distribution and designed so the connectors are interchangeable with other nonpower-limited sources located on the same premises.
Any junction and mating connectors must be constructed and installed to guard against people having inadvertent contact with live parts. These circuits must not be installed with any other power circuits
Tomi Engdahl says:
Intro to Class 4
Fault Managed
Power Systems
https://www.necanet.org/docs/2023necabicsisummitlibraries/default-document-library/powerpoints/intro-to-class-4-fault-managed-power-systems—stephen-eaves.pdf?sfvrsn=a1e661ac_3
Quick Review of Circuit Classes
• Class 1, Class 2, and Class 3 circuits are differentiated from
each other by power limitations
• Class 2 considers safety from a fire initiation standpoint and provides
acceptable protection from electric shock
• Class 3 considers safety only from a fire initiation standpoint
Class 2 and 3 Circuits are Limited Energy
Circuits
• Limits possibilities of ignition or ventricular fibrillation
• Devices and systems must be LISTED as a Limited Power
Source (LPS)
• Power over Ethernet (PoE) is a well-known example of Class 2
VoltServer: The Pioneer of Fault Managed Power
• The only company with a fault managed power system
• Eight years of commercial deployments under NEC and CEC Article 725
• Participated in industry groups to develop UL 1400-1 and 1400-2
• Resulted in the codification of Class 4 in the 2023 version of NFPA 70 Article 726
Benefits of FMPS
• Safe – NRTL certified for same wiring practices as Ethernet/PoE
• Significant Power – hundreds of Watts per pair of conductors
• Significant Distance – thousands of feet
• Skinny Conductors – 16-18AWG Typically
• System Monitoring and Control – remotely manage your power
distribution, take actions upon external events
• Speed to Deployment – can be run in same pathway or Class2 or Class3
circuits, fiber or hybrid cables…….many jurisdictions do not require permits
• Sustainable – smaller cable gauges, no conduit, intelligent control over
power use
FMPS Shock Faults
• FMPS not only limit fault energy for
shocks that occur between the line
conductor and earth, but they also
limit the fault energy for line-to-line
faults.
• This means if someone accidentally
touches both lines, the system will
react to the fault and limit the
energy into the person.
• Traditional power systems
employing GFIs cannot react to line-
to-line faults because GFIs cannot
tell the difference between a person
in contact with the wires and the
load.
• FMPS can tell the difference
between the load and a person in
contact with the lines.
• FMPS also limit the risk of fire.
• This is accomplished by limiting the amount of energy into an arc fault as well as managing resistive faults
• FMPS detect or prevent dangerous arcs that can lead to fire, both line-to-line as well as in-line.
• Resistive faults are limited to 100W for line-to-line faults which limits the amount of heat that can be
generated to the same amount of heat allowed in a traditional Class 2 circuit
FMPS Summary
Fault Managed Power Systems (FMPS) provide the
power capability of a power circuit with the hazard
levels of a power-limited circuit enabling new ways of
distributing power
Class 2 and Class 4 circuits CAN share the same
cable, enclosure, or raceway.
Class 4 – Fault Managed Power (FMP)
• 2023 Edition of NFPA 70 has a new Article 726
• Limits the fault power in the circuit by
monitoring for faults and controlling the power
transmitted into the fault
• Based upon risks associated with electric
shock and fire hazards
• Defines current limits in terms of duration
based on the human body model, limit energy
and power available during a fault event
• Also requires Functional Safety – Analysis and
mitigation of safety-related component failures
and behavior under fault conditions
• Restart, over-voltage, over-current, etc.
Class 4 Deployments
Class 4 circuits will not be an enforceable method of installation
within a given authority having jurisdiction (AHJ) until that AHJ
has adopted the 2023 code.
It is expected to take several years before Class 4 circuits are
allowed by code within a majority of AHJ.
Tomi Engdahl says:
https://www.cablinginstall.com/home/webinar/14296151/august-24th-webinar-introduction-to-faultmanaged-power-systems-revolutionizing-power-delivery-for-structured-cabling?sti=CIM_BeldenVoltserverAug24Em3_WS_DK_08172023&pk=CIM_BeldenVoltserverAug24Em3_WS_DK_08172023&utm_source=CIM+Webcasts&utm_medium=email&utm_campaign=CPS230816054&o_eid=7211D2691390C9R&rdx.identpull=omeda|7211D2691390C9R&oly_enc_id=7211D2691390C9R
Tomi Engdahl says:
Vertical power delivery enables cutting-edge processing
https://www.vicorpower.com/resource-library/articles/vertical-power-delivery-enables-cutting-edge-processing?utm_source=electronicdesign&utm_medium=display&utm_campaign=l03_computing_prospecting_noram&utm_content=article_vertical_power_delivery_enables_cutting_edge_processing_personifai
To meet that perpetual need for HPC demands innovation and the ability to adapt and scale for tomorrow using modular power. The Vicor architectures are flexible enough to be adapted in a wide variety of high-performance computing scenarios. Leveraging an FPA, Vicor minimizes the “last inch” resistances by combining lateral power delivery and vertical power delivery.
Tomi Engdahl says:
https://www.uusiteknologia.fi/2023/10/09/eaton-ottaa-rittalin-modulaariset-datakeskukset/
https://etn.fi/index.php/new-products/15410-kolmivaiheista-ups-varavirtaa-raekistae