The cooling tower in the picture above must maintain a certain temperature perhaps
30°C (85°F) for the condenser water temperature. Looking at this example, see if you can
identify some of the functions that must be performed by the VFD, AC motor and fans? In
other words, what must the fans be able to do? Take a couple of minutes to jot down the
The fans must …
A few of the basic functions of an VFD in controlling the AC motor and fans are
covered on the pages that follow.