AC Motor VS DC Motor | Difference with Advantage and Disadvantage

AC Motor VS DC Motor

A motor is a machine which can convert electrical energy into mechanical energy. Both AC and DC motor do same work, both of them convert electrical energy into mechanical energy. We use both types of machine for different works. Both of the motors have their own advantages and disadvantage. Today we are going to discuss AC Motor VS DC Motor.

The electric motor which can run on AC supply is called AC Motor.

The electric motor which can run on DC supply is called DC Motor.

The working principle of AC motor and DC motor is different. 

DC Motor:

A simple DC Motor works in the principle that when we placed a movable current carrying conductor in a static magnetic field there will be an interaction between the magnetic field and the flux produced by the current carrying conductor hence a torque will be developed on the current carrying conductor and ultimately the conductor will start rotates whose direction will be according to Flemming's Left Hand Rule.

There are mainly two types of DC Motor,

1. DC Motor with Brush: In his type of motor we gives the DC supply to the motor armature winding through the brush and commutator arrangement. This type of motors are called simple DC Motors and they are working as I told you in the above paragraph.
2. Brushless DC Motor: This type of motors haven't any brush mechanism. This type of motor has very high efficiency. We already have an article on the Working of Brushless DC Motor. You can read that article. Although Brush less DC motor more expensive and it is not available in high power rating.

The speed equation of DC Motor is,

Here,

N = speed

V = supply voltage

Ia = Armature current

Ra = Armature resistance

φ = flux
k = constant

AC Motor:

There are two types of AC Motor,

1. Induction Motor: The Induction Motor works same as a Transformer. Like a transformer, the induction motor also has two winding only the difference that the secondary winding is rotating. When the AC supply is given to the stator winding of the motor an emf is induced in the rotor winding for the induction effect. The interaction of the rotor emf and the stator EMF creates a torque on the rotor and hence the rotor starts rotating. It is also called asynchronous motor as it always run at below the synchronous speed.
2. Synchronous Motor: In the synchronous motor the AC supply is given to the stator winding. The rotor of a synchronous motor may be consists of a permanent magnet or electromagnet. Remember that in case of the synchronous motor there is no induction effect. The interaction of stator flux and rotor flux(which created by permanent magnet or electromagnet) creates a torque on the rotor hence the rotor start rotating. As the motor run at synchronous speed it is called as Synchronous Motor.

The speed equation of AC Motor,

Here,
f = frequency
P = no. of poles

Difference between AC Motor and DC Motor:

SL NO.	AC(Alternating current) Motor	DC(Direct Current) Motor
1.	Required AC power supply to run.	Required DC power supply to run.
2.	The AC motor is Simple in construction than DC motor.	DC Motor is more complex in construction than AC Motor.
3.	The AC motor is light in weight than the same capacity of DC motor.	The DC motor is heavier than the same capacity of AC Motor.
4.	There is no commutator mechanism is present.	The DC motor has a commutator mechanism.
5.	Some types of  AC motor has a slip ring mechanism.	The DC motor has not any slip ring mechanism.
6.	The single-phase induction motor is not self-starting.	All types of DC motors are self-starting.
7.	Single phase induction motor works on Double Revolving theory.	Double revolving theory does not work on any type of DC motor.
8.	There is no extra mechanism is needed for creating a rotating magnetic field in three phase induction motor.	A mechanical or electronic switch is needed for creating a rotating magnetic field in brushless DC motor.
9.	According to the speed equation of the AC motor, the speed can be controlled by frequency, poles etc.	According to the speed equation of the DC motor, the speed can be controlled by the supply voltage, voltage drop across armature, flux etc.
10.	Losses in the AC motor is less than DC motor.	Losses in DC motor is more than the AC motor.
11.	The efficiency of the AC motor is greater than DC Motor.	The efficiency of the DC motor is less than AC motor.

Read Also: 

• [Explained] Motor Circuit Protection System and Devices
• Actual Difference between Servo Motor and Stepper Motor
• Actual Difference Between Synchronous Motor and Induction Motor
• Difference between Generator and Alternator Full explanation
• Applications and Advantages of all types of Motor- DC Motors, AC motors, Universal Motors

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