Types of synchronous machines :
According to the arrangement of armature and field winding, the synchronous machines are classified as rotating armature type or rotating field type.
In rotating armature type the armature winding is on the rotor and the field winding is on the stator. The generated emf or current is brought to the load via the slip rings. These type of generators are built only in small units.
In case of rotating field type generators field windings are on the rotor and the armature windings are on the stator. Here the field current is supplied through a pair of slip rings and the induced emf or current is supplied to the load via the stationary terminals.
Based on the type of the prime movers employed the synchronous generators are classified as
1. Hydrogenerators : The generators which are driven by hydraulic turbines are called hydrogenerators. These are run at lower speeds less than 1000 rpm.
2. Turbogenerators : These are the generators driven by steam turbines. These generators are run at very high speed of 1500rpm or above.
3. Engine driven Generators : These are driven by IC engines. These are run at aspeed less than 1500 rpm.
Construction of synchronous machines
1. Salient pole Machines : These type of machines have salient pole or projecting poles with concentrated field windings. This type of construction is for the machines which are driven by hydraulic turbines or Diesel engines.
2.Nonsalient pole or Cylindrical rotor or Round rotor Machines : These machines are having cylindrical smooth rotor construction with distributed field winding in slots. This type of rotor construction is employed for the machine driven by steam turbines.