The Open Rack 2.0 specification has been offered to partners in the Open Compute Platform (OCP) such as Facebook and Google will submit them to the OCP Foundation later in the year. This will be Google’s first submission to the OCP community, aiming to bridge the transition from 12V to 48V architecture with ready-to-use designs for 48V payloads.
“The proposed v2.0 standard will specify a 48V power architecture with a modular, shallow-depth form factor that enables high-density deployment of OCP racks into data centers with limited space,” says Debosmita Das, Technical Program Manager.
Google has developed a 48V ecosystem with payloads using 48V to Point-of-Load technology since 2010 and is now making the technology public through OCP. “Our contributions to the Open Rack Standard are based on our experiences advancing the 48V architecture both with our internal teams as well as industry partners, incorporating the design expertise we’ve gained over the years,” says Das.
In addition to the tool-less mechanical and electrical specifications for the racks, the specification includes details for the design of 48V power shelves, high-efficiency rectifiers, rack management controllers and rack-level battery backup units.
Control and management of the racks is via RS-485 or CAN to connect all the rectifiers in a daisy chain which can all be swapped while the rack is operating in a ‘hot swappable’, load sharing configuration. The rectifiers take an input from 200V to 240V AC or 200V to 277Vac and the output is programmable from 42V to 58 Vdc, with a default of 54.5V.
The peak efficiency has to be greater than 97.0% for loads of 30% to 100% and an input voltage of 230Vac, while the minimum efficiency at lower loads of 10 to 30% has to be 92%. This highlights the challenge for point of load module designers for lower load efficiencies.
The lithium ion battery system for the rack has to be hot swappable with an extra pack (N+1) for redundancy and has a microcontroller to monitor the condition and temperature. Google says this architecture has already saved it millions of dollars in energy costs in its data centers.
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