Thermally Controlled Fans Automatic speed control is available with many Nidec brushless dc fans. Fans with this optional feature respond to elevated temperatures by running faster and delivering increased air flow. All fans must be capable of providing a flow of air that will adequately cool components under conditions of greatest power dissipation and highest temperatures. When temperatures are lower, less air flow is required to do the same job. In most applications, worst-case design conditions exist only for a small percentage of total operating hours.
Air temperatures are usually lower than maximum design values.
Under these usual conditions, a cooling fan can adequately accomplish its task while operating at a speed slower than its worst-case design parameter. At slower speeds, a fan will make less noise and consume less power. Benefits of thermally controlled fan operation vary by application, but they can be significant. Normal operating circumstances might require only half as much cooling air. The workstation's configuration may vary so that operation dissipates less power than the design load.