Difference Between DC and AC Motors

• DC Motors
• AC Motors

1. OperatingSource

DC Motor

• DC motor operates on DC (Direct Current) and converts the electrical energy into mechanical energy.

AC Motor

• DC motor operates on DC (Direct Current) and converts the electrical energy into mechanical energy.

2. Main Types

DC Motor

• DC Motor has two main types named as :
  • Brushless DC Motor
  • Brush DC Motor

AC Motor

• AC Motor is divided into three main types :
  • Single Phase Motors (Also named as General Purpose Motor)
  • Double Phase Motors
  • Triple Phase Motors
• They are further classified as :
  • Synchronous AC Motors.
  • Induction AC Motors.

3. Basic Working Principle

DC Motor

• A simple DC motor contains a coil of wire that can rotate in a magnetic field provided by the permanent magnets.
• So when the coil placed in the magnetic field is provided with the current, a force is exerted on this coil which can be find by the Flemming's Right Hand Rule.
• This force generates a torque in the coil and the coil starts to rotate in the magnetic field as shown in the image below :

•  The current is provided to the coil through the brushes which are in contact with the split rings.
• The force produced in the coil of length 'L' placed in the magnetic field 'B' carrying a current 'i' is equal to iLBsin(theta) , where theta is the angle between 'B' and 'i'.

• When the coil surface comes in horizontal with the magnetic field, we can see that now torque becomes 0 , because current is zero at this point and also the brushes comes in the gap between split rings.
• At this point, no current is provided to the coil but coil still continue its motion because of its momentum and then again split rings come in contact and the process continues.

AC Motors

• AC motor works on the same principle as I have described for the DC motor, the only difference lies in the split rings.
• For AC motors we use continuous rings as shown in image below, they doesn't block the current and the current can move in both directions easily.
• Moreover, in most of the AC motors armature remains stationary and the magnetic field keeps on rotating.

4. Applications

DC Motors

• DC Motors are used where you want to controlled speed.
• It doesn't provide high energy so its used mostly where low energy is required.

AC Motors

• AC motors provide high energy that's the only reason AC motors are mostly used in industries.
• We can't control the speed of AC motor.