Introduction To Servo Motors: What Is Their Purpose?

Introduction To Servo Motors: What Is Their Purpose?

Whether your facility uses a lathe or plasma cutter, chances are there is a servo system at its heart. How else would we be able to have machinery that is responsive, efficient, and precise? And nestled at the heart of that servo system is a motor that powers the whole thing.

But what makes these motors different from other, similar types? How do they work, and why do we use them? That’s why we have prepared an introduction to servo motors and what their purpose is.

The Origin of Servo Motors

Finding the origin of servo motors isn’t as straightforward as one would think. The electric motor was a pre-Victorian era invention, with Thomas Davenport, a Vermont blacksmith, inventing the first battery-powered motor in 1834. These initial motors were limited in their power capacity and how much work they could do.

However, the term servo motor originally didn’t refer to an electric motor, but one powered by steam and found on ships called “Le-Servomoteur” or “slave-motor.” This type of system was an early form of the feedback system and allowed sailors to ensure the position of the rudder reflected the position of the wheel.

Servo Drives: A Review of the System

An understanding of servo motors requires an understanding of the systems that they power. Servo systems, as we mentioned, are the force powering automatic control systems, such as computer numerical systems.

This is how they work.

  • A worker keys in a command into an interface panel. This panel can save commands and operations to be used later.
  • From here, a controller takes the command and translates it to data that the system can use.
  • Once the command has been translated, a drive takes the command and controls the system’s tool movements, including the exact speed and power.
  • The servo motor powers the tool, enabling it to perform these commands.
  • As the tool mills, drills, or cuts, an encoder device sends feedback to the system, allowing the tool to adjust throughout the process.

This system has a plethora of benefits, namely accuracy. The closed-loop nature of the system allows it to adapt on the fly, helping mitigate some of the effects of human error on manufacturing processes.

The Purpose of Servo Drives Within Servo Systems

The other parts of the system—the interface panel, controller, drive, and tool—are what allow servo systems to be precise. But it is the motor that allows the system to be powerful. It is what transforms electrical energy into the mechanical energy needed by a servo system.

Taking the motor out of the system is no different than taking the engine out of a car. It doesn’t matter how many bells and whistles the car has—automatic braking, Bluetooth—it won’t go anywhere without its engine.

Characteristics of a Servo Motor

Speed Range

As we have seen, a servo system has to be adaptable by nature. Otherwise, it wouldn’t be able to take the feedback from the encoder and adjust as needed. So, the motor powering such a system has to be able to adjust with the rest of the system.

That’s why servo motors have such a wide speed range, ranging from as low as .1 RPM to as high as 5,000 RPM. This wide range allows the motor to provide the speed necessary for a wide variety of applications.

Response Speed

Another aspect of this is how quickly the motor can respond to commands. After all, if the encoder sends feedback to the drive, the whole system will need to shift immediately, or else the tool it is trying to manufacture may be ruined.

Along with being able to move at high speeds, servo motors are some of the most responsive motors of their type. This makes them well-suited for their processes.


Torque and speed are often confused by those new to the world of motors. Instead of measuring how quickly a motor moves or rotates, torque measures the amount of twisting force a motor generates. This helps determine how great a load a motor can bear.

Some motors—stepper motors, for example—have a high torque when the motor is running at a low speed. Unfortunately, this torque diminishes as the motor’s speed increases. Servo motors have a high torque even at higher speeds. This makes them ideal for large-scale, high-speed production.

Types of Servo Motors

Sticking with the car analogy from earlier, we can keep in mind that different cars have different types of engines, depending on what the driver wants out of them. For instance, a smaller car may use a three-cylinder engine, while a racecar might use an eight-cylinder engine. The same concept applies to servo motors.

When it comes to servo motors, you find two main varieties: AC and DC motors. Similarly, this differentiation refers to how we power the motor.

AC Servo Motor

AC stands for alternating current. It is when the flow of electricity alternates between a negative or positive charge. This is the type of electricity that we find in electrical outlets. These motors tend to be less efficient power-wise, but they’re stable, lower weight, and require less maintenance than their DC counterparts.

DC Servo Motor

DC, on the other hand, stands for direct current. This is electricity that flows in only one direction—this is the type you find in batteries. Battery-powered servo motors are often heavier, noisier, and require more maintenance. However, they make up for it in being efficient and providing a higher overall power output.

Industries That Use Servo Motors

No introduction to the purpose of servo motors would be complete without looking at the way they have revolutionized the industries they are part of. You can find servo motors in any industry that uses CNC machinery and other equipment that uses servo motors. A few key industries of this type include:

  • Manufacturing
  • Photography
  • Warehouse and storage
  • Robotics
  • Aerospace
  • Automotive
  • Medical and pharmaceutical
  • Textiles

As we mentioned, early motors were limited in their capacity. However, as servo motors and the feedback systems they were attached to began to expand, new possibilities opened up.

With greater power and accuracy, industries have been able to expand both how much they can produce and the complexity of the machinery they could produce. This has allowed servo motors to be used when building anything from a new car to a satellite positioning system.

Servo motors are everywhere. And at Industrial Automations, our wide collection of CNC servo drives is sure to be able to meet your facility’s needs.

Introduction To Servo Motors: What Is Their Purpose?