Synchronous machine has following important parts
The stator is outer part of the machine It is the stationary part of a synchronous machine. The stator contains following parts.
It is an outer body of a machine. It is made up of cast iron. It protects the inner parts of the machine. The stator core is placed in between the frame. Cast iron is used for the construction of the stator frame because it has high mechanical strength.
The material of a stator core is laminated silicon steel. It is made from number of stamping which are insulated from each other. Laminations are used to reduce eddy current losses and silicon steel is used to reduce hysteresis losses. The function of stator core is to provide an easy path for magnetic flux. The slots are cut on its inner periphery to accommodate the winding.
Stator winding is placed in the slots. Enameled copper is used as winding material.
The rotating part of the machine is called Rotor. From a construction point of view, there are two types of rotors named as
- Salient pole type rotor
- Non-salient pole type rotor
Salient Pole Type Rotor
Salient pole type construction is suited for medium and low speed synchronous generators. In this case, projected poles are provided on the rotor. These rotors are usually employed at hydroelectric plants. The speed of these machines is quite low. These rotors are designed with larger diameter and small axial length. The exciting current is supplied by an exciter in fixed on each alternator shaft.
Non-Salient Pole Type Rotor
Non-salient pole type construction is suited for the higher speeds. In this case, the rotor is made of silicon steel laminations. These rotors are used for high speed alternators. These rotors have a smaller diameter and larger axial length. These types of rotor give noiseless operation and better in dynamic balancing. About 2/3 of the rotor pitch is slotted, leaving 1/3 for the pole centre. The speed may be as high as 3000 r.p.m at 50Hz.