While both A.C. and D.C. motors serve the same function of converting electrical energy into mechanical energy, they are powered, constructed and controlled differently.
The most basic difference is the power source. A.C. motors are powered from alternating current (A.C.) while D.C. motors are powered from direct current (D.C.), such as batteries, D.C. power supplies or an AC-to-DC power converter.
D.C wound field motors are constructed with brushes and a commutator, which add to the maintenance, limit the speed and usually reduce the life expectancy of brushed D.C. motors. A.C. induction motors do not use brushes; they are very rugged and have long life.
The speed of a D.C. motor is controlled by varying the armature winding’s current while the speed of an A.C. motor is controlled by varying the frequency, which is commonly done with an adjustable frequency drive control.
The maintenance cost of the AC Motor is more as compared to that of a DC Motor.
n an AC Motor, there are three input terminals known as RYB (Red, Yellow and Blue). In DC Motor, there are only two terminals. They are known as Positive and Negative.
AC Motors are not self-starting, and thus, it requires some external equipment to start the motor initially. DC Motor are self-starting motors.
The difference between the AC motor and DC Motor is given below in the table form: