Also known as AC drives, variable frequency drives (VFD) are essentially controllers capable of driving electric motors, something accomplished by varying the voltage and frequency that goes into an electric motor.
AC Motor of Variable Frequency Drives
A variable frequency drive system uses an AC electric motor. Typically, this is a three-phase induction motor although a single-phase motor is also used on occasion. The benefit of a three-phase induction motor is that it works for most purposes and typically, it is the more cost-efficient solution. Keep in mind that when induction motors experience increased voltage stresses supplied by variable frequency drives, there has to be a design in place for definite-purpose inverter-fed duty.
Benefit of Energy Saving
A number of different load applications for a fixed speed motor supplied directly from AC line power save energy when operated with a variable frequency drive and at variable speeds. The cost of savings is most notable in variable torque centrifugal fan and pump applications. In this case, both power and torque vary with cube and square in coordination with speed. As a result, a significant reduction of power occurs.
In the US, experts estimate that up to 65% of electrical energy used goes specifically for motors. Of that, 75% is for compressor loads, as well variable torque fan and pump. In addition, 18% of energy that goes to the approximate 40 million motors within the United States could be saved by using variable frequency drives, as well as other efficient energy technologies. However, of AC motors in the US, just 3% have AC drives.
Performance is also bolstered with variable frequency drives. These drives have the ability to increase quality for flow, acceleration, pressure, speed, monitoring, tension, torque, and temperature in both commercial and industrial applications. These drives are capable of running a motor in a very specialized pattern, which in turn minimizes stress electrically and mechanically. The result is usually smoother acceleration and deceleration, among other things.
Remember, there are many different topographies pertaining to variable frequency drives such as voltage source inverter, current source inverter, loan commutated inverter, matrix converter, six-step inverter, and double-fed slip recovery system.