Difference Between Ac And Dc Motor
The difference between AC and DC motors is very important not only from an examination point of view but also for various projects and practical demonstrations.
By knowing the difference between AC and DC motors, choosing the right motor for a particular monitor becomes easier. For engineering aspirants too, this topic is of great interest.
In this article, the detailed difference between DC and AC motors is explained in tabular form for easier understanding.
Before understanding the differences between DC and AC motors, it is important to understand the basics of electric motors. By knowing the details of the electric motor, one can easily understand the differences and communicate easily. For more information on the motor, see Electric motor and see specifications.
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 which 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, 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 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. |
This was the main difference between AC and DC motor. AC and DC motors are widely used in various household appliances.
Knowing the specific differences between AC and DC motors can help an individual to select one of them as per the requirements. For more information on related topics, see the articles given below.
What is slip called in a Motor?
How to supply Power to the Rotor?
Power is supplied to the rotor, or motor, directly from a direct current source in a DC motor, while power is supplied to the device by stimulating rotation in an AC motor.
What are the losses in DC motor?
There are three types of losses in DC motor, and they are:
- Mechanical loss: This loss refers to the friction which is caused due to brush and bearings and due to other rotating parts.
- Iron loss: This loss occurs due to eddy current and hysteresis.
- Copper loss: This loss mainly occurs in the armature and in the field windings.