Electricity & Megnetism

Difference between AC motor and DC motor in tabular form

difference between ac motor and dc motorThere are two types of electric motors, AC motors, and DC motors. The basic difference between ac motor and DC motor is that AC motor powers on AC current while DC motor powers on DC current, To learn in detail about AC and DC motor comparison table is given below about the difference between AC and DC motor.

Difference between AC motor and DC motor in tabular form

        AC Motors

  DC Motors

Ac motors are powered from AC current.DC motors are powered from DC current.
In AC motors conversion of current is not required.In DC motors conversion of current is required like ac into dc current.
AC motors are used where power performance is sought for extended periods of time.DC motors are used where motor speed required to be controlled externally.
AC motors can be single-phase or three phases.All DC motors are single phase.
In AC motors Armatures do not rotate while magnetic field continuously rotates.In DC motors, the armature rotates while the magnetic field does rotate.
Repairing of DC motors is costly.Repairing of AC motors is not costly.
AC motor does not use brushes.DC motor uses brushes.
AC motors have a longer life span.DC motors have not longer life span.
The speed of AC motors is simply controlled by varying the frequency of the current.The speed of DC motors is controlled by varying the armature winding’s current.
AC motors require effective starting equipment like a capacitor to start operation.DC motors do not require any external help to start operation.

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We learn more about ac motor and dc motor in detail.

What is an AC motor?

The AC  motor’s stator has coils which are supplied with the AC current and produces a rotating magnetic field. The AC  motor’s rotor rotates inside the electric motor’s coils and attached to the output shaft that produces torque by the rotating magnetic field.

How does an AC motor work?

There are two types of AC motors. Synchronous motors and asynchronous motors.

The synchronous motor consists of a rotor which is energized by DC supply. The stator has the 3 phase winding from which power can be supplied. Now when these two supplies are given, that is at certain voltages, current is drawn and the coil inside produces the magnetic fields. When the AC rotating field (though the stator does not rotate, the 3 phase field will give the effect of rotation)and the DC field interact, torque is produced which leads to the rotation.

The induction motor or asynchronous varies in just a single part. It does not have a separate DC field. Instead, the rotor rotates by the effect of inductance or transfer of flux. The rotor will try to follow the 3 phase flux in the stator and hence the rotary. This motor is used in fans.

What are the types of an AC motor?

There are basically two different types of AC  motors and each of them uses a different type of rotor.

  1. Synchronous motors
  2. Asynchronous motors or induction motors

The synchronous motor is able to operate with precision supply frequency because it does not reply on induction. The magnetic field on a synchronous motor is generated by current delivered through slip rings. Synchronous motors run faster than induction motors because the speed is reduced by the slip of the asynchronous motor. An induction motor uses a magnetic field on the rotor of an induction motor that’s created by an induced current.

Types of synchronous motors

  • Plain synchronous motors
  • Super synchronous motors

Types of induction motors

  • Single-phase
  • Three-phase

How many types of DC motors?

There are two types of DC motors.

  • Brushed DC motors
  • Brushless DC motors

Types of brushed DC motors

  • Shunt wound
  • Compound wound
  • Permanent magnet
  • Series Wound

Conclusion:

AC motors and DC motors use the same principle of using an armature winding and magnetic field except with DC motors. In AC motors the armature does not rotate and the magnetic field continuously rotates.

In some applications, DC  motors are replaced by combining an AC motor with an electronic speed controller.DC  motors are replaced with an AC  motor and an electronic speed controller because it is a more economical and less expensive solution.

DC  motors have many moving parts that are expensive to replace, and DC electric repair is usually more expensive than using a new AC motor with an electronic controller.

So as far as maintenance is the concern, AC motors are used mostly as easy availability of AC supply DC motor has a constant maintenance problem.

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