Difference between Servo Motor and DC Motor

An electric motor is an electromechanical energy conversion device which converts the electrical energy input into mechanical energy output in the form of rotation of shaft.

Based on the types of electric supply and working, the electric motors are classified in many types such as DC motors, induction motors, synchronous motors, stepper motors, servo motors, and many more.

Read through this article to find out the major differences between a servo motor and a DC motor. But, before discussing the differences, let's get a basic overview of servo motors and DC motors.

What is a Servo Motor?

A type of electric motor that functions as a rotary actuator and allows for a precise control of angular velocity, position and acceleration is known as servo motor.

A servo motors consists of a sensor for position feedback on their rotor to control its position and speed at all times. Thus, the servo motors are generally characterized by their closed-loop control system design.

The servo motors can be of two types namely AC servo motors and DC servo motors. Where, the AC servo motors are used in large applications, while DC servo motors are used in small electronic devices like robotic joints, camera autofocus system, antenna positioning systems, CNC machine, etc.

What is a DC Motor?

As its name suggests, a DC motor is the type of electric motor that converts the electrical energy in form of direct current (DC) into mechanical energy (rotation of shaft).

The DC motors have two types of constructions namely brushed DC motor and brushless DC motor. But, when we use the keyword DC motor, it simply means that we are talking about brushed DC motor.

A DC motor consists of a stator part which forms the magnetic field system and a rotor part that acts as the armature of the motor. A commutator is also mounted on the shaft of the rotor. The commutator segments are connected to the ends of the armature winding. The carbon brushes are used to make the electrical contact with the commutator and the armature. Therefore, in order to start the DC motor, a direct current is allowed to pass into the armature winding through the commutator and brushes.

The electric current flowing through the armature winding produces a magnetic field which interacts with the magnetic field of stator to produce a torque on the rotor. Due to this torque, the rotor spins to produce output mechanical energy at the shaft.

The DC motors are commonly used in electronic devices, cranes, toys, elevators and lifts, power tools, and in many other appliances.

Difference between Servo Motor and DC Motor

The following table highlights all the significant differences between a servo motor and a DC motor −

Basis of Difference Servo Motor DC Motor
Definition A servo motor is a rotatory actuator that allows for a precise control of angular position, velocity and acceleration. A DC motor is a type of electrical machine that uses electrical energy to convert it into mechanical energy for driving a mechanical load.
Number of wires There are three wires in a servo motor namely power, control and ground. DC motor has only two wires namely power and ground.
System components The assembly of a servo motor involves four major parts: a suitable motor, gearing set, position sensor (encoder) and a control circuit. In case of DC motor, there is only an individual DC machine with no extra components.
Speed The speed of servo motors is high, typically from 1000 RPM to 6000 RPM. DC motors have moderate speed, it depends on the type of the motor.
Control mechanism Servo motors involve complex control mechanism. However, they are highly controllable. The control mechanism of DC motors is simple. We just need to reverse the leads to change the direction of rotation and change the voltage to change the speed.
Efficiency The efficiency of servo motors is high. The efficiency of DC motors is average and comparatively less than that of servo motors.
Suitability Servo motors are most suitable for intermittent applications. DC motors are suitable for continuous applications.
Reliability Servo motors are highly reliable. The reliability of DC motors is moderate.
Cost Servo motors are relatively expensive. DC motors are less costly than servo motors.
Applications Servo motors are extensively used in industrial automation, robotic joins, camera autofocus systems, and many other positioning systems. DC motors are used to drive mechanical loads. These are widely used in cranes, elevators, lifts, toys, kitchen appliances, etc.


The most important difference that you should note here is that a servo motor is used in positioning systems, while a DC motor is used to drive the usual mechanical loads.