The correct answer is: A. synchronous motor has no slip.
A synchronous motor is a type of electric motor that runs at a constant speed, synchronized with the frequency of the power supply. This is in contrast to an induction motor, which has a variable speed that depends on the load.
The main reason why a synchronous motor has a better power factor than an induction motor is because it has no slip. Slip is the difference between the speed of the rotor and the speed of the stator field. In an induction motor, slip is always present, and it can be as high as 5%. This means that the rotor is not always rotating at the same speed as the stator field, and this causes current to flow in the rotor. This current is called “slip current,” and it is responsible for the poor power factor of an induction motor.
In a synchronous motor, there is no slip, because the rotor is always rotating at the same speed as the stator field. This means that there is no slip current, and the power factor of a synchronous motor is much better than that of an induction motor.
The other options are not correct because:
- Option B is incorrect because the stator supply is required to produce the magnetic field in both synchronous and induction motors.
- Option C is incorrect because the mechanical load on the rotor does not affect the power factor of the motor.
- Option D is incorrect because the airgap does not affect the power factor of the motor.