# Difference between VFD and VSD

**URL:** <https://forumautomation.com/t/difference-between-vfd-and-vsd/14198>\
**Category:** Electrical\
**Tags:** vfd\
**Created:** [June 16, 2026, 4:58am UTC](https://forumautomation.com/t/difference-between-vfd-and-vsd/14198 "2026-06-16T04:58:01Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Rabert](https://forumautomation.com/user_avatar/forumautomation.com/rabert/32/6784_2.png) [@Rabert](https://forumautomation.com/u/Rabert)\
**Post date:** [June 16, 2026, 4:58am UTC](https://forumautomation.com/t/difference-between-vfd-and-vsd/14198/1 "2026-06-16T04:58:02Z")

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## Difference between VFD and VSD

In modern industrial automation & motor control systems the terms

- Variable Frequency Drive (VFD) and
- Variable Speed Drive (VSD)

are often used interchangeably.

However they are not exactly the same.

Understanding the key difference between VFD & VSD is important for selecting the right motor control solution for all the industrial applications.

## What is a Variable Frequency Drive (VFD)?

A **[Variable Frequency Drive (VFD)](https://forumelectrical.com/working-principle-of-variable-frequency-drive-vfd/)** is an electronic device that is used to control the speed & torque of an AC motor by varying the frequency & voltage supplied to the motor.

By adjusting the output frequency a VFD allows accurate motor speed control, improved energy efficiency & reduced mechanical stress on equipment.

## What is a Variable Speed Drive (VSD)?

A Variable Speed Drive (VSD) is a common term used for any device that controls the speed of a motor.

A VSD can include

- VFDs,
- DC drives,
- Hydraulic drives,
- Mechanical drives and
- Other speed control technologies.

## Difference between VFD and VSD

## VFD vs VSD

The primary difference is that a VFD controls motor speed by changing the electrical frequency supplied to an **[AC motor](https://forumelectrical.com/3-phase-ac-motor-alternating-current-motor-troubleshooting/)** whereas a VSD refers to any method utilized to vary motor speed regardless of the technology employed.

 ![4](https://cdn.forumautomation.com/original/2X/3/3a3371c110d3f27b5adfdc8649d15896dd6880a5.jpeg)

| **Parameter** | **Variable Frequency Drive (VFD)** | **Variable Speed Drive (VSD)** |
| --- | --- | --- |
| Definition | A VFD controls the speed of an AC motor by varying the supply frequency and voltage. | A VSD controls the speed of a motor using any speed-control technology. |
| Scope | A VFD is a specific type of motor drive. | A VSD is a broad category that includes various drive technologies. |
| Motor Compatibility | A VFD is mainly used with AC motors. | A VSD can be utilized with AC motors, DC motors and other drive systems. |
| Operating Method | A VFD changes the frequency of the electrical supply to the control speed. | A VSD uses electrical, mechanical, hydraulic, or electronic methods to control speed. |
| Technology | A VFD uses frequency-conversion technology. | A VSD may use multiple speed-control technologies. |
| Application | A VFD is primarily used for AC motor speed control. | A VSD is used wherever variable motor speed is required. |
| Energy Efficiency | A VFD provides high energy savings in variable-load applications. | The efficiency of a VSD depends on the technology being used. |
| Examples | AC Drive, Inverter Drive, Frequency Converter. | VFD, DC Drive, Hydraulic Drive, and Mechanical Variable-Speed Drive. |
| Cost | A VFD is generally cost-effective for AC motor applications. | The cost of a VSD varies depending on the drive type. |
| Relationship | Every VFD is considered a VSD. | Not every VSD is a VFD. |