Why does synchronous motor develop torque only at synchronous speed?

As stated in Chapter 1, this is because synchronous motors can develop a torque only when running at the synchronous speed. Once the rotor reaches a speed close to the synchronous speed (>95\%) through some starting means, the field winding will be excited, so the motor locks into synchronization.

Why synchronous machine does not produce torque at any other speed?

A synchronous motor is one in which the rotor normally rotates at the same speed as the revolving field in the machine. If the rotor speed is made equal to that of the stator field and there is no load torque, these two magnetic fields will tend to align with each other.

Why is the synchronous reluctance motor always run at synchronous speed?

The rotor needs to be rotated at a speed near to the synchronous speed during starting. If done so, the rotor poles get magnetically coupled with the rotating stator poles, and thus the rotor starts rotating at the synchronous speed. Synchronous motor always runs at a speed equal to its synchronous speed.

Why is synchronous motor not self-starting what methods are generally used to start the synchronous motors?

Synchronous motors have lots of advantages but being not self-starting unlike 3 phase induction motors, is a major disadvantage. In synchronous motors, the stator has 3 phase windings and is excited by 3 phase supply whereas the rotor is excited by DC supply. Due to this, the motor cannot start on its own.

Why does an induction motor never run on synchronous speed?

An induction motor always runs at a speed less than synchronous speed because the rotating magnetic field which is produced in the stator will generate flux in the rotor which will make the rotor to rotate, but due to the lagging of flux current in the rotor with flux current in the stator, the rotor will never reach . …

Why the speed of the motor is less than the synchronous speed?

Actual speed of the induction motor will be less than the synchronous speed. The reason for this is if the armature turns exactly at synchronous speed, then the magnetic field of the stator windings no longer cuts the rotor windings. Under this condition, no current would be induced to the rotor windings.

What is synchronous torque?

the torque that acts on the shaft of a synchronous machine when the rotational speed of the rotor deviates from the synchronous speed and that keeps the machine in synchronism.