The Difference Between VFD and Servo Drives Explained

The Difference Between VFD and Servo Drives Explained

When it comes to choosing equipment for our businesses, our first thoughts are often about power. The machinery’s motors have to be powerful enough to perform the necessary functions for it to be a wise acquisition. The forces that control the motors are equally as important as the motors themselves.

When it comes to CNC machinery, that force is often a servo drive. But for other machinery, you may find yourself looking at a motor with a variable frequency drive. Having the difference between VFD and servo drives explained will help you make a well-informed decision for your company.

What are Servo Drives and Variable Frequency Drives?

Servo Drives

Servo drives are part of larger servo systems. The servo drive takes the commands that operators input into a control panel and amplifies them. The motor and tool carry out the drive’s commands while an encoder provides feedback. The drive processes the feedback and gives new commands accordingly.


Variable frequency drives control the speed of an AC motor by using diodes and transistors to convert AC and DC electricity. They also use a capacitor to filter electricity between conversions. Typically, VFD operators use VFDs to change motor speed manually—though they can potentially use PLC devices as well.

What Are the Differences Between VFD and Servo Drives?

Type of Motors

Servo drives and VFDs work with two different types of motors. Servo drives tend to work with permanent magnet motors, which use rare earth magnets. VFDs use a type of induction motor called squirrel cage motors. Permanent magnet motors tend to have a higher magnetic flux, giving them higher torque.

Use of an Encoder

However, the AC motors that VFDs operate are often too simple to perform the complex functions PLCs and encoders require. Because of that, encoders are far more common on servo drives.

How To Choose a Drive for Your Application

Which drive you choose depends on the needs of your facility. A servo drive is ideal if you’re doing large-scale production that requires more power, complicated functions, and high precision. However, VFDs are a better choice if you’re emphasizing energy efficiency in your operations.

Whichever you choose, Industrial Automations has VFDs and servo drive amplifiers fit for your company’s needs.