Difference between Synchronous motor and Induction motor

Synchronous Motor

3Φ Induction Motor

Hammond self starting synchronous motor.jpgBy MePaJa – Own work, CC BY-SA 4.0, Link Silniki by Zureks.jpg
By Zureks – Own work, CC BY-SA 3.0, Link
Synchronous motor is a doubly excited machine which requires a DC excitation at the rotor. Its stator is excited using an AC supply. It is a singly excited machine. No excitation for the rotors. The stator windings are excited using an AC source.
Synchronous motor is not a self-starting motor. It is required to provide some auxiliary means to reach the synchronous speed. An induction motor is a self-starting motor.
Speed of the motor remains constant. The motor speed is independent of the load. It always runs at synchronous speed from no load to full load condition. The Speed of induction motor is always less than the synchronous speed, N < Ns. Motor speed decreases with the increase in load.
 A synchronous motor can be made to operate from lagging power factor to leading power factor just by changing its excitation. An induction motor operates at lagging power factor.
A synchronous motor is costlier than an induction motor of similar rating. An induction motor is cheaper than the synchronous motor of similar ratings.
It has a complicated construction. It is simple in construction.
More efficient than the induction motor. Less efficient compared to the synchronous motor.

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