Power supply standards: Which way forward?
Patrick Le Fèvre of Ericsson Power Modules deliberates on the advantages and challenges facing the new standard in power supply.
There is little doubt about the many advantages of the emerging 380V (400V peak) DC power standard that is expected to become commonplace in data centres and in other telecom and datacom networking facilities over the next few years. Rather than the traditional AC supply, or the 48V DC supply line used widely in the telecom industry, there are many driving factors to move to this new standard including improved system efficiency, reduced cooling and air-conditioning, lower energy consumption, higher power and equipment densities, and increased reliability and availability.
A reduced number of power units can mean lower TCO (Total Cost of Ownership) in terms of operating and capital expenditures. Another factor is the increasing employment by data centres and network operators of renewable energy sources such as from photovoltaic among others, which already deliver a DC supply.
One further advantage is the possibility of establishing a single and well-defined power interface, irrespective of the availability of equipment from telecom (48V DC) or datacom (230V AC) vendors, and of providing the foundation for a common strategy for different types of equipment used in Information and Communication Technology (ICT) markets. Supported by Ericsson Power Modules, much work has already been done. Standards for 380V DC power systems have been developed by the European Telecommunications Standards Institute (ETSI), including EN 300 132-3-1, which defines the bus voltage between 260V and 400V, and ETSI EN 301 605, which defines earthing and bonding arrangements, as well as contributions from the International Telecommunication Union (ITU-T), the International Electrotechnical Commission (IEC), and the Emerge Alliance.
The standards define commercial building power system infrastructures that provide power distribution for a telecom and/or data centre operation within the building. The infrastructure will include a voltage bus and connectors to distribute power to telecom equipment, computers, servers, storage devices, and networking devices, in addition to backup batteries, lighting, fans, and cooling equipment.
But all of this brings a few questions concerning the many step-down options and/or intermediate bus voltages. Many suggest the most economical way is to convert the 380/400V DC down to 48V DC, because of the large quantity, or arguably critical mass, of equipment already in the telecoms world based on a 48V DC supply. Certainly, this appears to be a highly attractive solution.
However, it could also be that for some equipment used in specific applications, operators may decide to step down to a much lower voltage—for 19in rack systems, for example. Many are saying these rack systems should be powered by the 380V line stepped down to 12V (also a commonly used intermediate bus voltage used in telecom).
But what is the best conversion topology to go from 400V to 12V that guarantees high efficiency and also meets isolation requirements? It is certainly a large step-down in a single leap. Should it be implemented in multiple step-down DC/DC conversions via 48/54V for example? Or should the industry be looking at powering 1V-core-voltage processors direct from a 400V DC line?
Test-systems based on 380V DC have been running for many years now in applications across the globe. They have confirmed savings in both energy consumption and cost. There is growing consensus that it is a pretty good idea. Now we just need to work out the details.
Patrick Le Fèvre
Ericsson Power Modules
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