Difference between AC and DC motor

AIP shares with you the "Difference between AC and DC motor".

September 13, 2023

Difference between AC and DC motor

A motor is a device that converts mechanical energy into electrical energy, so a motor is a motor that converts electrical energy into mechanical energy. These motors can run on either AC or DC power. Therefore, there are two main types of motors: AC motors and DC motors.

There are many differences between AC motors and DC motors. The most obvious difference is the type of current that each motor converts into energy, alternating current for AC motors and direct current for DC motors. AC motors are known for their higher power output and efficiency, while DC motors are prized for their speed control and output range.

Difference between ac and dc motor

The following table is about the differences between AC motors and DC motors:

serial number

Differentiating attributes

             AC motor

                                       DC motor



An AC motor can be defined as an electric motor driven by alternating current (AC).

A DC motor is a rotating electric motor that converts direct current (direct current energy) into mechanical energy.



There are two main types of AC motors: synchronous AC motors and induction motors.

There are also two main types of DC motors – brushed DC motors and brushless DC motors.


Current input

AC motors only run on input AC power

A DC motor only operates when DC power is supplied. For DC series motors, the motor may run on AC power. However, with parallel motors, the motor is never run on AC power.


Commutator and brushes

There are no commutators and brushes in AC motors.

There are commutators and carbon brushes in the DC motor.


Input power phase

AC motors can operate on single-phase and three-phase power.

DC motors can only operate on single-phase power.


Motor starts

Three-phase AC motors are self-starting, but single-phase AC motors require a starting mechanism.

DC motors are always self-starting in nature.


Armature characteristics

In an AC motor, the armature is stationary while the magnetic field rotates.

In a DC motor, the armature rotates while the magnetic field remains stationary.


Input terminal

In AC motors, there are three input terminals (RYB).

In a DC motor, there are two input terminals (positive and negative).


speed control

The speed of an AC motor can be changed by changing the frequency.

For DC motors, the speed can be controlled by changing the armature winding current.


load change

AC motors respond slowly to load changes.

DC motors exhibit a rapid response to load changes.


life expectancy

Since AC motors have no brushes and commutators, they are very tightly assembled and have a high life expectancy.

The brushes and commutator in a DC motor limit speed and shorten the motor's life expectancy.



AC motors are less efficient due to induced current losses and motor slip.

DC motors are highly efficient because there are no slip or induced current losses.



AC motors require less maintenance due to the absence of brushes and commutators.

DC motors require excessive maintenance due to the presence of brushes and commutators.


Application areas

When high speed and variable torque are required, AC motors are used.

When variable speed and high torque are required, a DC motor is used.


the real function

They are mainly used in large industries. For example: water heater, lawn, garden equipment, etc.

They are mainly used in small household appliances. For example: electric wheelchairs, handheld sprayers and pumps, coffee machines, off-road equipment, etc.

This article concludes that AC motors are used for their best output power performance, reliability, and less maintenance requirements. DC motors are used because they are easier to control speed and direction. But their frequent maintenance costs are very high.

The above are the main differences between AC motors and DC motors. Both AC and DC motors are widely used in various electrical appliances. Understanding the detailed differences between AC and DC motors can help one choose one of them as per the requirements. To know more about motor-related topics, visit the article given below.

Types of motors

Nine Common Causes Of Motor Failure

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BLDC motor tester

Universal motor tester
AC motor tester

AIP motor tester

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