Consider the following statements about cylindrical type synchronous generators and select the most appropriate option.

Question

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SSC JE Electrical 14 Nov 2022 Shift 3 Official Paper

The number of poles under such a constructional framework is higher and thus suitable for gas turbines.
The number of poles under such a constructional framework is less and thus suitable for hydraulic and oil turbines only.
The constructional framework is suitable for hydraulic, steam and gas turbines.
The number of poles is relatively less and thus suitable for steam turbines.

Answer 1

Types of the rotor in synchronous generators

1.) Cylindrical rotor

F2 Savita Engineering 25-7-22 D49

The cylindrical pole has fewer poles generally 2 or 4 poles.
These are high-speed rotors as the weight is less due to less number of poles.
The number of poles is relatively less and thus suitable for steam turbines.
These rotors have a uniform air gap.
They are smaller in diameter but have a longer axial length.

2.) Salient pole rotor

F2 Savita Engineering 25-7-22 D48

The salient pole rotor has a large no. poles generally 6 or 8 poles.
These are low-speed rotors as the weight is more due to less number of poles, but more weight provides better mechanical stability.
These rotors have a non-uniform air gap.
Salient pole rotors are large in diameter and shorter in length.
Salient pole rotors normally require damper windings to avoid oscillations of rotors during operation. They are mostly used in hydropower plants.