Variable Frequency Drives (VFDs) are mechanical forms of variable speed drives, also known as adjustable speed drives. A VFD allows motor-based systems to adjust the speed at which the motor runs. That speed is based on how much power the mechanical systems need to meet the demand of the building. The demand of the system is also referred to as the “load” of the system. By varying the speed the motor is able to meet the needs of the load without using more energy than necessary.
Nearly all Variable Frequency Drives work on the basis of taking the existing AC supply, converting it to DC using a rectifier, and then converting it back to a variable frequency supply using an inverter. The inverter is the key part of this, so a variable frequency drive is sometimes simply called an inverter.
Currently, VFDs are being built into many new systems; however, they can also be added to some current systems through a retrofit. When looking to retrofit a system with a drive, consult a professional to match the drive with the existing system and motor. Making sure they are properly matched is very important in making sure you gain the highest efficiency possible.