Difference between AC and DC Motor

An electric motor is an electromechanical energy conversion device that converts electrical energy into mechanical energy. An electric motor consists of two major parts namely, the stator and the rotor. The stator is a station part of the motor, and it is usually the outer frame of the motor. Whereas, the rotor is a rotary or movable part of the motor. Rotor has a shaft to which the mechanical load is connected.

There are several types of electric motors such as AC motors, DC motors, synchronous motors, induction motors, etc.

In this article, we will discuss the important differences between DC motors and AC motors. But before that let's have a look into the basics of AC and DC motors individually.

Introduction to AC Motor

The type of electric motor which uses an alternating current supply to work is called an AC motor or alternating current motor. In other words, an ac motor is a type of electric motor that converts AC electrical energy into mechanical energy.

There are two types of ac motors namely, induction motors and synchronous motors.

An induction motor is a type of asynchronous ac motor whose rotor runs at a speed slightly less than the synchronous speed (i.e. speed of the rotating magnetic field). While a synchronous motor is a constant-speed ac motor whose rotor runs at a fixed speed which is equal to the synchronous speed.

AC motors are the most widely used electric motors in industries and homes to drive different mechanical loads like fans, washing machines, compressors, mills, etc.

Introduction to DC Motor

The type of electric motor which converts DC electrical energy into mechanical energy is called a DC motor or direct current motor.

A DC motor consists of two parts namely the stator and the rotor. Where, the stator forms the magnetic field system of the motor, while the rotor forms the armature of the motor. Hence, a DC motor has a constant and fixed magnetic field and rotating armature. To establish a connection between the stationary dc power source and the rotating armature, a commutator-brush assembly is used.

Based on the connection of armature and field system, there are three types of dc motor namely, series dc motor, shunt dc motor, and compound dc motor.

DC motors are used in specialized applications such as electric vehicles, electric trains, cranes and hoists, etc.

Difference between DC Motor and AC Motor

The following table gives the important differences between AC and DC motors:

AC Motor	DC Motor
An electric motor that converts ac electricity into mechanical energy is called an AC motor.	An electric motor that converts dc electrical energy into mechanical energy is called a DC motor.
AC motor requires an alternating current source to work.	DC motor requires the direct current source to work.
AC motors are of two types namely, induction motors and synchronous motors.	DC motors are of three types namely, series dc motor, shunt dc motor, and compound dc motor.
AC motor has two terminals (if single-phase motor) namely, line and neutral, or three terminals (three-phase motor) namely line terminals.	DC motors always have two terminals namely positive and negative.
AC motor has a stationary armature.	DC motor has a rotating armature.
AC motor does not have a commutator.	DC motor has a commutator.
The speed of ac motors is controlled by changing the supply frequency.	The speed of dc motors is controlled by changing the armature current and magnetic flux.
AC motor provides a smooth and noise-free operation.	DC motors produce more noise and generate a spark at the brush-commutator contact surface.
All AC motors are not self-starting.	DC motors are always self-starting.
In AC motors, the armature is stationary, while the magnetic field rotates.	In DC motors, the armature rotates, while the magnetic field remains stationary.
AC motors are relatively long-lasting.	DC motors have a comparatively short life span.
The maintenance cost of AC motors is less.	The maintenance cost of DC motors is high.
AC motors require less maintenance.	DC motors require frequent maintenance.
AC motors are less efficient due to electromagnetic induction losses, motor slips, etc.	DC motors are more efficient because there are no slip and induction losses.
AC motors are suitable for high-speed and variable torque applications.	DC motors are suitable for variable speed and high torque applications.
AC motors are widely used in industries to drive mechanical loads.	DC motors are used in toys, electronic devices, and some special industrial loads.

Hence, this is all about the differences between AC motors and DC motors.