How do VFDs work?

A variable frequency drive, or VFD, is an adjustable speed drive used to control an electric motor by varying the frequency and voltage supplied to the motor.  The speed of the motor is controlled by either increasing or decreasing the voltage of the VFD.

In a VFD, electricity is forced through a converter.  The converter is made of six diodes which allow current flow in one direction.The diodes open and close based on how much current is flowing through them. A VFD has two converters that convert AC to DC and DC to AC. One converter is called a diode bridge converter and the other, an inverter. A VFD is different from other drives because it allows users to generate any necessary frequency. This is accomplished by closing one or more of the switches on the drive.

Variable frequency drives all have essentially the same parts that make them work. Each has a cooling fan, a DC bus, AC power output, heat sink and other components.

If you have ac motors that need a variable output, you need to install variable frequency drives.  If you are not using VFDs you are wasting energy and throwing away money!  Because electric motor systems use so much electricity, installing a VFD can cut costs by up to 70%.  Installing a VFD can help to reduce maintenance and downtime and help equipment last longer.


Schneider VFDs
Posted in Energy, General

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"How does a Variable Frequency Drive (VFD) work?"

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