How to tell the Difference Between A Servo Controller and A Servo Drive or Amplifier

Yaskawa Legend 01 Servopack

Have you ever noticed that the terms servo controller, servo drive, and servo amplifier are often used interchangeably? This can be confusing! The likely cause of confusion between the terms is that they typically are the reason motors move the way they do. However, servo controllers and servo drives or amplifiers serve different functions in servo motors and are in no way alike. So, let us clear that up. 

Here is the explanation in very basic terms:

  • Technically, the Servo Drive (also called a Servo Amplifier) provides power to the Servo Motor. The Servo Amplifier takes low voltage commands for torque, speed, or position, then amplifies them into a high-powered format that the servo motor can use. 

The Servo Controller, on the other hand, is responsible for sending commands that dictate how and when the servo motor will move. 

The Servo Controller provides the specific command to the amplifier through analog signals or data. For example: Move 10 feet at a rate of 20 feet per minute. The Servo Amplifier takes that signal and provides the necessary power for the time required to accomplish that task. It does this while constantly monitoring the feedback from the Encoder. It has enough onboard control circuitry to interpret control and feedback signals.

Simply put, the servo controller feeds information to the servo amplifier through signals. The amplifier uses this information to influence what the motor does, how it does it, and when it happens. The key difference between the servo motor and the servo drive or amplifier is their distinct functions.

Can Servo Drives Function as Motor Controllers?

Servo Drives and Motor Controllers

Here’s where it gets a bit trickier – the Servo Amplifier and Servo Controller are sometimes incorporated into ONE device. This is likely the reason why these two terms get interchanged. Generally, they are independent units – one for control and one for power and feedback.

However, motors depend on servo drives to provide an element of control; as such, they could sometimes be considered controllers. Some analog servo drives, for instance, have built-in offset potentiometers which can be used to adjust the gain, and, in such cases, they will function as controllers. Additionally, some digital servo drives have the built-in processing power, making them work independently without external controllers. However, adjusting and tuning are not control inputs for the motors, as this is only possible with servo controllers. 

Therefore, as blurry as the lines may be when differentiating servo drives from servo controllers, one thing is clear, they function distinctly. 


Anilam servo amplifier SA-301A

For example, this recently repaired Anilam servo amplifier SA 301A  (Drive) provides power to multiple motors (multiple axes).

Anilam controller CC-516F

The above Anilam servo amplifier (Drive) is connected to this repaired Anilam controller CC 516F that provides the commands for each axis.

Now that we’ve cleared that up, you might have more questions!

What If they Get Damaged? Are they Repairable?

In this example, both of these units were repairable. Typically, the servo amplifier has a slightly higher repair success rate than the servo controller, but both are often repairable. The controller is more complicated and often contains several levels of OEM proprietary programming. If not catastrophically damaged, the amplifier has a higher repair success rate. When considering whether to repair or replace, it is always best to get a qualified industrial electronic repair service to evaluate your damaged servo amplifiers (drives) and servo controllers.

Do you have questions or concerns about your servo controller or amplifier, or do you think it may need service? If it’s still under warranty, contact your OEM. Contact an independent industrial electronic repair center if it is out of warranty. They should offer free evaluations for your servo controller and if needed, a free quote for repairs. They should also provide repair reports and a good warranty covering parts and labor.

Contact ACS Industrial for All Your Industrial Repair Needs

ACS Industrial is an independent industrial electronic repair center providing repair services for servo amplifiers and servo controllers of all types and most all manufacturers, including Anilam repairs, as well as servo drive repairs, AC/DC drives, VFD drives, servo motors, encoders, printed circuit board repairs, monitors and touchscreens, PLCs, test equipment, and much more. Our customer service team is available to answer your questions and help solve your industrial electronic repair concerns. Legacy equipment can be repaired! RUSH Service is available. You can reach them by calling 800-605-6419