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Enhance Redundancy Counter-Rotating Fan Control Scheme for Cooling During a Fan Failure in an Electronic Enclosure

IP.com Disclosure Number: IPCOM000237075D
Publication Date: 2014-May-29
Document File: 5 page(s) / 96K

Publishing Venue

The IP.com Prior Art Database

Abstract

Described is an enhanced redunancy counter-rotating fan control scheme for cooling during a fan failure in an electronic enclosure.

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This is the abbreviated version, containing approximately 33% of the total text.

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Enhance Redundancy Counter -

-Rotating Fan Control Scheme for Cooling During a

                    Rotating Fan Control Scheme for Cooling During a Fan Failure in an Electronic Enclosure

Late model electronic enclosures produced have become densely populated; both physical density and power density have increased in folds. The amount of cooling required has, in turn, also increased without significant parallel gains in the design of the air mover tasked to provide the necessary cooling. Granted, the air movers can be run at higher speeds to provide the additional cooling required; however, it comes at the expense of added fan power consumption and higher acoustical noise levels, both of which have approached compliance and regulated asymptotes. The use of counter-rotational axial fans has proliferated through many designs with many benefits with few apparent cons. However, when multiples of this type of air movers are used in parallel within an electronic enclosure, designing for cooling redundancy can become challenging, as these types of small air movers can deliver very high airflow pressure heads.

    Counter-rotating fans usually have airflow and static pressure which is higher than two conventional DC axial fans of the same size connected in series. These fans consist of one body housing two motors which drive two independent rotors which spin in opposite rotational directions and can be run at different speeds. Depending on the specific design of the fan, one of the two rotors can be weaker than the other; if ran on its own, the weaker rotor would produce less airflow and static pressure. Together, both rotors produce more airflow and static pressure than the mathematical addition of their independent performance. For this reason, counter-rotational fans are sometimes favored over the use of two conventional axial fans connected in series.

    The challenge of using counter-rotation fans in very dense electronic enclosures can be unexpected redundant cooling design issues and thermal response with the traditional programmable fan control scheme. Conventional fan algorithms for providing adequate redundant cooling during a fan failure has been to default all remaining air movers within the electronic enclosure to their maximum speeds to compensate for the loss of performance of the failed fan. In systems with a push-pull fans arrangement, it acceptable to have the remaining good fans increase speeds to compensate for the loss of cooling. However, with the proliferation use of counter-rotating fans, increasing fan speeds to the maximum performance of these fans can overwhelm and swamp the surviving rotor in the counter-rotating fan body with the failed rotor, in most cases, severely limiting the amount of airflow and static pressure that it can produce, resulting in static airflow movement or, in extreme cases, reverse airflow through the fan. These conditions present major thermal and cooling concerns; while 90% of the electronic enclosure's component...