Difference Between AC and DC Motor

AC vs DC Motor 

An electromechanical device converts electrical energy to mechanical energy. AC motor is an electromechanical device that works on AC electricity while the DC motor works on DC electricity.

More about AC motor

An AC motor consists of two main parts a rotor, a component that rotates, and a stator, which is stationary. Both have coil windings to create a magnetic field and the repulsion of the magnetic field creates the rotor to move. The current is delivered to the rotor through slip rings, or permanent magnets are used. The kinetic energy of the rotor delivered to shaft connected to the rotor and the torque generated act as the driving force of the machinery.

There are two main types of AC motors. Induction motor, which runs more slowly than the frequency of the source, is the first type. The synchronous motor is designed to avert this effect of induction; therefore runs at the same frequency or a sub-multiple of the frequency.

AC motors can produce a large torque. Because of the power source used, it can be designed to draw large amounts of power. Power mains can supply very large currents required for the operation of the heavy duty motors. Most common AC motors use the squirrel cage rotor, which is found almost in all domestic and light industrial AC motors. Most domestic appliances like a washing machine, dishwasher, standalone fan, record player, etc. use some variant of a squirrel cage rotor.

AC motors are designed for three phase, two phase, and single phase power sources. Depending on the requirement the usage of the motor type varies.

More about DC motor

Two types of DC motors are in use; they are the Brushed DC electric motor and Brushless DC electric motor. The fundamental physical principle behind the operation of DC and AC motors are the same.

In brushed motors, brushes are used to maintain electrical connectivity with the rotor winding, and internal commutation changes the polarities of the electromagnet to keep the rotational motion sustained. In DC motors, permanent or electromagnets are used as stators. In a practical DC motor, the armature winding consists of a number of coils in slots, each extending for 1/p of the rotor area for p poles. The number of coils in small motors may be as low as six, and it may be as high as 300 in large motors. The coils are all connected in series, and each junction is connected to a commutator bar. All coils under the poles contribute to torque production.

In small DC motors, the number of windings is low, and two permanent magnets are used as the stator. When higher torque is needed the number of windings and magnet strength are increased.

The second type is brushless motors, which has permanent magnets as the rotor and electromagnets are positioned in the rotor. A high power transistor charge up and drives the electromagnets.

What is difference between AC motor and DC motor?

• AC motor works on AC electricity while DC motor works on DC electricity.

• General DC motors deliver less torque power than the AC motors.

• AC motor requires a starter mechanism, but the DC motors do not need a starter mechanism.

• DC motors are single phase motors whereas AC motors are both 1 and 3 phases.