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Difference Between AC and DC Motor

The difference between AC and DC motor 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 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 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 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 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 DC supply is given. In the 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 the 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 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.

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Keep visiting BYJU’S for more such difference articles and other physics articles.

Frequently Asked Questions – FAQs

What is slip called in a motor?

Slip is defined for an induction motor 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?

In a DC motor power is supplied to the rotor that is to the armature directly from the direct current source while in AC motor, power is supplied by inducing rotation to the device.

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.

What is a universal motor?

A universal motor is an electric motor that can operate either on an alternating current supply or on a direct current supply. A universal motor is also known as an AC series motor and is very much similar to the DC series motor. It has an armature winding and field windings connected in series. The direction of the torque remains the same irrespective of the polarity and this is achievable because the field flux and armature current are reversed simultaneously.

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