VFD Drives: What Do You Need To Know?

A variable frequency drive (VFD) is a device that helps to control the speed and torque of an AC motor through electronic means. They are used in industrial applications for many different purposes, but one of their most common uses is as an automatic tool changer for machine tools. In this article, we will break down what you need to know about VFD drives and how they work so that you can decide if they’re right for your application!


Variable Frequency Drives (VFDs) are used to control the speed of motors. The output of a VFD is proportional to the input signal. They are used for industrial, domestic and commercial applications.

VFDs come in a variety of types:

  • Constant Torque – These drives produce constant torque at variable speeds by controlling the motor current with respect to frequency;
  • Constant Horsepower – These drives produce constant horsepower at variable speeds by controlling the motor current with respect to frequency;
  • Variable Torque – These drives produce variable torque at constant speeds by varying their frequency; and
  • Variable Horsepower – These drives produce variable horsepower at constant speeds by varying their frequency

Working Principle.

Variable frequency drives (VFDs) are used to control the speed of a motor. Even when the load on a motor varies, the VFD will keep it running at a constant speed by adjusting its frequency accordingly. The frequency of AC supply is controlled by a VFD using semiconductor switches and sophisticated software algorithms.

Control Inputs.

  • Control Inputs: Control inputs are the inputs that a VFD uses to control the speed of the motor. For example, a VFD may have two control inputs: one for increasing speed and one for decreasing speed. When you send power to these two controls, it will send power to your motor in order to operate it at either high/fast or low/slow speeds.
  • Power Inputs: The power input is how your VFD receives electricity from its source of power (a wall outlet). This is where you plug in your extension cord so it can get enough power from an outlet to run properly on its own!

Vfd Drives

The Advantages of VFD Drives.

There are many advantages of VFD drives over their predecessors.

  • Reduced energy consumption: The main advantage of a VFD is the reduction in energy use, which can be as much as 40%. The reason for this lower usage is that motors can operate at full load while they are idle, thus saving themselves from overheating. This means that you don’t need to run your fans so frequently or install more powerful ones to keep the motor cool. You also get a better return on investment since you pay less on electricity bills and maintenance costs.
  • Lower maintenance costs: With a VFD system installed in your industrial equipment, you won’t have to worry about frequent repairs or breakdowns since it reduces vibration and heat generation by up to 60%. This means that there will be less wear and tear on moving parts such as belts and bearings, resulting in fewer replacements later down the line.
  • Reduced noise pollution: Because these devices feature soft start/stop functionality (which means they don’t start up abruptly) instead of sudden starts like those old mechanical rotary switches did before them), they reduce noise pollution significantly when compared side-by-side with traditional machines powered by DC drives (which didn’t offer any type of soft start feature).

A VFD is a device that can be used to control the speed of motors. They are mainly used in electric motors, and they are capable of changing the speed of the motor by changing its frequency. You can control the speed of your electric motor with the help of a VFD drive and save energy as well as money on your monthly bill.

There are two types of VFDs: fixed-speed and variable-speed drives. The former only lets you adjust the flow rate while maintaining constant speeds, while the latter lets you choose any speed that is suitable for your use case.


In this article, we’ve looked at the working principle of VFD drives, control inputs, and the advantages and disadvantages of these drives. You can easily control the speed of a motor with a VFD drive. The drive uses two or three-phase AC input to generate DC voltage, which is then converted into variable frequency current (VFC) by using an inverter circuit. 

This kind of drive has many advantages over conventional DC motor speed control systems, such as reduced noise generation due to soft start function and less wear on equipment due to lower temperature rise caused by friction between bearings during operation at various speeds.