What are Variable Speed Drives (VSD) and what are their benefits?
A variable speed drive (VSD) or variable frequency drive is a system for controlling the rotational speed of an AC electric motor by controlling the frequency of the electrical power supplied to the motor. Variable speed drives are also known as adjustable frequency drives (AFD), variable frequency drives (VFD), 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. VSDs save energy as the power provided to the motor is reduced according to load. For example, using a drive with a 30 kilowatt (kW) motor running 5,000 hours a year to control the air flow in a ventilation system brings an annual saving of 76,500 kW hours of electricity compared with regulating the flow rate by adjusting a damper.
