A variable-frequency drive (VFD) is a system
for controlling the rotational speed of
an alternating current (AC) electric motor
by controlling the frequency of the electrical
power supplied to the motor. A variable
frequency drive is a specific type of adjustable-speed
drive. Variable-frequency drives are also
known as adjustable-frequency drives (AFD),
variable-speed drives (VSD), AC drives,
microdrives or inverter drives. Since the
voltage is varied along with frequency,
these are sometimes also called VVVF (variable
voltage variable frequency) drives.
drives are widely used. In ventilation systems
for large buildings, variable-frequency
motors on fans save energy by allowing the
volume of air moved to match the system
demand. They are also used on pumps, elevator,
conveyor and machine tool drives.
Drives save energy by reducing power consumed
by motors driving centrifugal pumps, fans
and other rotating equipment. By controlling
the speed of a motor, the amount of energy
used by the machinery is optimized.