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Differences Between VSD, VFD, VVVF Explained

One of the most perplexing questions in the electrical world revolves around VSD/VFD/VVVF devices.

Are there any differences between these devices, or are they essentially all the same thing?


The acronyms AC and DC describe two electrical currents which control different types of motors. Electrical motors use both AC and DC power.

AC is an alternating current and the normal mains power is 240 / 415 volts, referred to as low voltage.

DC, in contrast, is used mostly in extra low voltage circuits, solar applications or batteries because it’s a different current.


VSD is the acronym for variable speed drive. This all-encompassing term describes drives which are used for controlling both AC and DC motors, and technically, even mechanically control.

It’s commonly used in the context of AC or DC electric drives.


VFD is the term for a variable frequency drive. It refers explicitly to electronic drives which control the speed of AC motors through adjustment of voltage and the frequency delivered to motors.

The terms VFD and VSD are commonly interchanged.


The acronym VVVF is used most often in the mining industry to refer to variable voltage variable frequency drives.

Both VVF and VFD describe the same AC drive. Any AC drive that works to automatically control voltage to adapt to the frequency which it is running at.


To further add to confusion, identical devices in the mechanical services / HVAC industry are also regularly referred to as frequency inverters, or inverters.

Again, these terms refer predominantly to AC drives.

Which should I use?

Industrial control systems are most commonly AC-powered.

In this instance, the three acronyms are interchangeable because they refer to the same thing.

When it comes to a DC control system, VSD is most likely the correct term.

In the mechanical services and HVAC industries, AC can also be called inverters.

Same Same but Different!

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1 Comment

Challaturu Team
Challaturu Team
Jul 20, 2023


These terms – VSD (Variable Speed Drive), VFD (Variable Frequency Drive), and VVVF (Variable Voltage Variable Frequency) – are all related to the control systems for electric motors, but they refer to slightly different aspects or types of control.

VSD (Variable Speed Drive): This is a general term for any drive that can control the speed of a motor. It includes several types of drives, such as VFDs, DC drives, mechanical variators, and servo drives.

VFD (Variable Frequency Drive): A Variable Frequency Drive (VFD) is a specialized variant of a Variable Speed Drive (VSD) that modulates the speed of an AC induction motor by adjusting the frequency and voltage of the electrical power it supplies. Due to its effectiveness…

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