Difference Between AC and DC Motor

 Difference Between AC and DC Motor

Sl. No.	Differentiating Property	AC Motor	DC Motor
1	Definition	An AC motor can be defined as an electric motor that is driven by an alternating current (AC).	A DC motor is also a rotatory electric motor that converts Direct current (DC energy) into mechanical energy.
2	Types	AC motors are mainly of two types – synchronous AC motors and induction motors.	DC motors are also mainly of two types – 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 a DC supply is given. In the case of an DC series motor, the motor might run with an AC supply. But, for shunt motors, the motor never runs on an 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) are 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 the case of DC motors, speed can be controlled by changing the armature winding 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 the AC motor is less.	The efficiency of the 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.