The difference between AC and DC motors is extremely important not only from the examination point of view, but also for various projects and practical demonstrations. By knowing the AC and DC motor differences, 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 is given in tabular form for easy understanding.
Before knowing the difference between DC and AC motors, 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 the electric motor, and check out the related details.
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. |
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.
Related Articles:
| Electromagnetic Induction | Relation Between Line Voltage And Phase Voltage |
| The Electric Generator | Magnetic Effects of Electric Current |
Keep visiting BYJU’S for more such difference articles and other physics articles.
Frequently Asked Questions – FAQs
What is slip in a motor?
For an induction motor, slip is defined as the difference between the synchronous speed (Ns) of the rotating field and the rotor speed N. It is expressed as the percentage of synchronous speed Ns.
How to supply power to the rotor?
Power is delivered to the rotor, or armature, directly from the direct current source in a DC motor, whereas power is given to the device via inducing rotation in an AC motor.
What are the three types of losses in a DC motor?
There are three types of losses in a 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.
Why is AC current better than DC?
Very adaptable system. It can use transformers to supply electricity to loads across long distances. AC generators are stronger and easier to manufacture than DC generators. Brushes and commutators are required for DC generators to create DC current.
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