Types of rotor in synchronous motor

Types of the rotor in asynchronous motor

 Synchronous motors have two types of rotor

• salient pole rotor
• nonsalient pole rotor

Salient pole rotor

A salient pole rotor consists poles projecting of from the surface of the rotor core and that’s why it is called a salient pole rotor. it is used in low and medium-speed electrical machines. The poles are fixed and are made of steel laminations to reduce eddy current losses. they have a non-uniform air gap. Poles of identical dimensions are assembled by stacking laminations to the required length. The air gap is maximum in between the poles and it is minimum under the pole centers. They have a short axial length and a large diameter. The pole shoes cover about ⅔ of the pole pitch.

Non-salient pole rotor

The non-salient rotor is also known as a smooth cylindrical type because of its construction. It is used in very high-speed applications like turbo-alternators. There are no projected poles. By the current flowing through the rotor, exciting winding poles are formed. The surface is smooth due to the absence of the projection of poles.

Cylindrical Rotors have the following parts.

• Rotor Core
• Rotor Winding
• Pole Core and Pole Shoe
• Spider
• Field Winding
• Damper Winding
• Rings