Difference Between AC and DC Motor

Difference between AC and DC motor is extremely important not only from examination point of view but also for various projects and practical demonstrations. By knowing the AC and DC motor difference, choosing the right one for a particular demonstration becomes easy. For engineering aspirants also, this topic holds extreme importance. In this article, the detailed difference between DC and AC motors in tabular form is given for easy understanding.

Before knowing the difference between DC and AC motor, it is important to know the in-depth details about an electric motor. By knowing the details of an electric motor, one can easily understand the differences and relate the points comfortably. To learn more about motors, visit electric motor and check out the related details.

Difference Between AC and DC Motor

Sl. No.

Differentiating Property

AC Motor

DC Motor

1

Definition

AC motors can be defined as an electric motor which is driven by an alternating current (AC).

DC motors is also a rotatory electric motor which converts Direct current (DC energy) into mechanical energy.

2

Types

AC motors are mainly of two types which are synchronous AC motors and induction motors.

DC motors are also mainly of two types which are namely DC motors with brushes and DC motors without brushes.

3

Current Input

AC motors only run when an alternating current is given as input.

DC motors will only run when DC supply is given. In case of DC series motor, the motor might run with AC supply. But, for shunt motors, the motor never runs on AC supply.

4

Commutators and Brushes

Commutators and brushes are absent in AC motors.

Commutators and carbon brushes are present in the DC motors.

5

Input Supply Phases

AC motors can run on both single phase and three phase supplies.

DC motors can run only on single phase supply.

6

Starting of Motor

A three-phase AC motor is self-starting but a single-phase AC motor requires a starting mechanism.

DC motors are always self-starting in nature.

7

Armature Characteristics

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

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

8

Input Terminals

In AC motors, three input terminals (RYB) is present.

In DC motors, two input terminals (positive and negative) are present.

9

Speed Control

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

In case of DC motors, speed can be controlled by changing the armature winding’s current.

10

Load Change

AC motors show a slow response to the change in load.

DC motors show a quick response to the change in load.

11

Life Expectancy

Since AC motors do not have brushes and commutators, they are very rigged and have a high life expectancy.

The brushes and commutators in DC motors limit the speed and reduce the life expectancy of the motor.

12

Efficiency

Due to induction current loss and motor slip, the efficiency of AC motor is less.

The efficiency of DC motor is high as there is no slip and induction current loss.

13

Maintenance

AC motors require less maintenance as brushes and commutators are absent.

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

14

Applications

AC motors are required where there is a need for high speed and variable torque.

DC motors are required where there is a need for variable speed and high torque.

15

Practical Uses

They are mainly used in large industries.

They are mostly used in small domestic appliances.

These were the main differences between AC and DC motors. Both AC and DC motors are used extensively in various appliances. Knowing the detailed AC and DC motors differences can help an individual to choose either of them according to the requirements. To learn more about their related topics, visit the articles given below.

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Practise This Question

A particle of mass 1 kg is projected upwards with velocity 60 m/s. Another particle of mass 2 kg is just dropped from a certain height. Find out the acceleration and the velocity of COM after 2 s when neither of the particles has collided with the ground.