According to the design of rotor poles, synchronous generators are divided into,
1. Salient Pole
More commonly used in smaller and medium power ranges is the salient-pole generator and are usually coupled with hydraulic turbines as most hydraulic turbines have to turn at low speeds as large number of poles is required on the rotor.
2.Non Salient Pole / Cylindrical/ Turbo
The largest generators used in major power stations are usually cylindrical generators. They operate at high speeds and are usually directly coupled to a steam or gas turbine.