Types of Alternator

Alternators or synchronous generators can be classified in may ways depending upon their application and design.
According to application these machines are classified as
1) Automotive type – used in modern automobile
2) Diesel electric locomotive type – used in Diesel Electric Multiple Unit
3) Marine type – used in marine
4) Brush less type – used in electrical power generation plant as main source of power
5) Radio alternators – used for low brand radio frequency transmission

These ac generators can be divided in many ways but we will discuss now two main types of alternator categorized according to their design. These are1) Salient pole type 
It is used as low and medium speed alternator. It has a large number of projecting poles having their cores bolted or dovetailed onto a heavy magnetic wheel of cast iron or steel of good magnetic quality. Such generators are characterized by their large diameters and short axial lengths. These generator are look like big wheel. These are mainly used for low speed turbine such as in hydral power plant.
2)   Smooth Cylindrical type
It is used for steam turbine driven alternator. The rotor of this generator rotates in very high speed. The rotor consists of a smooth solid forged steel cylinder having a number of slots milled out at intervals along the outer periphery for accommodation of field coils. These rotors are designed mostly for 2 pole or 4 pole turbo generator running at 36000 rpm or 1800 rpm respectively.