Browse Prior Art Database

Two Speed Control in Multi-Fan Cooling Systems

IP.com Disclosure Number: IPCOM000112835D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Gaunt, DS: AUTHOR [+2]

Abstract

Described is a method of sensing the failure of a fan in a multi-fan cooling system by each of the remaining fans without the need for interconnection between fans or remote sensing.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 56% of the total text.

Two Speed Control in Multi-Fan Cooling Systems

      Described is a method of sensing the failure of a fan in a
multi-fan cooling system by each of the remaining fans without the
need for interconnection between fans or remote sensing.

      In redundant cooling systems, e.g., those with multiple fans,
failure of a fan can be compensated for by increasing the rotational
speed of those that remain.  Sensing a fan failure is accomplished by
monitoring the rotational speed of a fan.  The rotational speed is a
function of the pressure difference between the inlet and outlet.
This relationship is depicted in the Figure.

      The change in fan speed resulting from the failure of one fan,
which in this example is about 100 RPM, can be sensed within each of
the remaining fans using a Halls-effect transistor.  Logic circuitry
within each fan can monitor the rotational speed and, when this
change occurs, can individually switch the fans to their higher
operating speed.

      In a system operating at its higher speed with one failed fan,
replacement with a good unit will result in a further increase in the
speed of the remaining fans which can be sensed by the control
circuit and the fans switched back to their normal operating speed.
An additional feature of this design is that a reduction in the
system's airflow impedance, which might arise when a device is
removed from the system, will cause the fan speed to drop.  This
change in speed, seen by all of the fa...