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news / 2004 |
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| Is AdvancedTCA Cool Enough? |
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| September 24 , 2004 – Waterloo, Ontario |
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One of the major differences between traditional and the new generation telecommunication equipment isgreater heat release and larger footprints. In this article Eike discusses the latest requirements for AdvancedTCA cooling and the solutions that are evolving to meet these needs.
Introduction
The heat release per unit volume continues to increase due to denser packaging and higher clock speeds. The AdvancedTCA shelves are targeting 2.8KW for a 14-slot shelf and 3.2KW for a 16-slot shelf resulting in equipment frames with a total heat release of well over 10KW (at four shelves in an UTF). See the soon to be published T1E1.8 Project 41, “Engineering Requirements for a Universal Telecommunication Framework (UTF).” The footprint and floor loading of many non-traditional framework and aisle spacing must increase due to:
Revised shelf functionality (Rear Transition Modules)
Heat release
Cable and airflow management
To put this in perspective, a portable room heater dissipates 1.5KW.
What about the existing specifications?
GR-63-CORE
It has been recognized that the Heat-Release Objectives in the Telecordia™ NEBS GR-63-CORE needed an update. Furthermore, the exact assumptions for the NEBS GR-63-CORE standard became unclear, as new types of telecommunications equipment and air-distribution systems had been introduced.
GR-3028-CORE
The GR-3028-CORE includes Heat-Release Targets (HRT). Equipment Rooms need to do a better job of matching these targets to ensure continued network reliability. Figure 1 depicts the main cornerstones of GR-3028-CORE and how they are interrelated.
Figure 1
PICMG 3.0 AdvancedTCA, Section 5, “Thermal”
The majority of equipment installed in central office (CO) and data centers today is air cooled due to simplicity, relative low cost, reliability, and ease of implementation. This trend is likely to continue in the future for the same reasons. The thermal guidelines in this specification apply to air cooling, but other cooling methods are permissible although not covered in this specification. Boards, shelves, and frames may be cooled by forced convection with the assistance of fans or blowers.
Figure 2 depicts the implementation of a pull-air concept in an AdvancedTCA Shelf.
Shown in Figure 2 are:
Four RiCool-2 blowers
Backplane
Card Guide/EMI barrier
Typical cable tray
Air-in sensor
ShMC redundant/hot swap
Forced convection shelves that rely upon fans or blowers should be designed to operate with a single fan/blower in failure and continue operating under the specified thermal environment. The key to surviving a fan/blower failure is to have redundancy or extra capacity, the ability to monitor and detect fan/blower failure, and the ability to repair/replace failed fans/blowers either live or during scheduled down time.
However, the airflow direction for air entering/exhausting the frame is nonstandard and considered beyond the scope of this standard. The choice of frame is left to the system integrator and end user requirements.
Changing needs often fuel innovation
Innovation has been a constant with the changes in telecommunications technology. Initially convection cooling was the preferred cooling method, typically in central office environments. This was followed by relatively low noise forced air cooling requirements of typically 30W/slot VME systems where existing fan technology was available. When there was a requirement for redundant High Availability (HA) in CompactPCI systems at 55W/slot in an 8U 19-inch system, existing forced air cooling devices did not meet the need. At that time Rittal developed and successfully deployed its RiCool-1 range of blowers (110 cfm at 1.6-inch H 2 O) in CO applications. However, the recent requirements for AdvancedTCA cooling needs again exceeded available fan/blower capability. After extensive simulation and research, Rittal created the next generation of AdvancedTCA dedicated RiCool-2 blowers (Figure 3). This blower design follows the air pull-through concept, therefore benefiting from less back pressure and adding no additional (push concept fan/blower) generated watts to the air intake. Typically this adds an additional 280W to an AdvancedTCA shelf, an amount that is cut in half, if a push/pull concept is used).
Figure 3
This cooling device FRU has the built-in intelligence to detect a failure in the Base Management Controller (BMC) and/or Management Application (MA). Sensors (thermistors, hall-effect switches, voltage, etc.) will support all of the sensor device commands derived by the BMC and is interoperable with the AdvancedTCA Intelligent Platform Management Interface (dual IPMI).
One of the major advantages of this concept is serviceability. The cooling device comes as a self-contained AdvancedTCA cooling FRU (1U in height) in a box (COTS). By simply removing the front accessible blower cover from the AdvancedTCA shelf, a faulty blower can be removed without the use of tools. After re-attaching the blower cover to the shelf, the shelf remains fully operational (with the remaining three blowers running now at 100% speed), and this can be accomplished in seconds. The faulty blower may then be replaced later. Installation of the replacement blower is also a simple event done in seconds without a tool, and once installed the blowers reset to approximately 70 percent of full speed automatically.
Removing 200W per slot (2.8KW) from an AdvancedTCA Shelf at 40 ° C ambient at approximately 65 dBA with a serviceable FRU solution was the goal at Rittal/Kaparel. We feel comfortable that we have been able to achieve this and will support this with a full simulation and actual measurements that are now being taken.
A thermal challenge
However, the desire in the industry to deploy three or even four such 2.8KW or 3.2KW AdvancedTCA shelves in a 600mm wide x 600mm deep x 44U frame (UTF) remains a thermal challenge. One must consider not only the cooling requirements, but also:
I/O and power cable management
RTM access
Optional seismic requirements
The need for security doors
Telecommunication equipment relies on the flow and control of electrical currents, and whenever electrical current flows heat is generated. Unless the cooling air can find a flow path to and from the components to be cooled, the circuit temperature will rise. If the airflow path is application optimal entering the frame, then entering the shelf, passing over the board, exiting the shelf, then exiting the frame, the temperature rises until it stabilizes at a point where heat flowing away from the circuit is equal to the heat generated by the electrical current flowing through the circuit. As noted at the beginning of this article, one of the main differences of the traditional and new telecommunication equipment is greater heat release resulting in and from larger footprints. |
About Kaparel |
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Kaparel is an ISO 9001:2000 registered company that develops, manufactures, and markets electronic packaging solutions and high-speed backplanes to the global Converging Communications market. From its pioneering work in CompactPCI bridge designs, Kaparel has quickly become a leader in many aspects of high-speed backplane architecture technology and has a library of over 500 high-speed custom designs including AdvanceTCA.
Kaparel’s catalog of product includes a complete line of high slot count, hot swap and high availability backplanes and high quality electronic packaging products and services for telecommunications and embedded computer manufacturers. Founded in 1996, Kaparel is based in Waterloo, Ontario - Canada’s Technology Triangle and is a part of Rittal International, the world’s largest electronic enclosure manufacturer with offices in over 55 countries. |
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Media Contact
Michael Pichna · Marketing Specialist · Kaparel Corporation
T: 519.725.0101 Ext.232 F: 519.725.0414 · E: marketing@kaparel.com · www.kaparel.com
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