Correct Answer - Option 3 : steam turbines
Explanation:
- In synchronous generators or alternator, generally salient-pole type of rotors is driven by hydro-turbines and cylindrical type rotors are driven by steam turbines
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Cylindrical rotors are used in high-speed alternators having speed between 1500 rpm to 3000 rpm and salient pole rotors are used in low-speed devices, from 100 rpm to 1500 rpm.
- Cylindrical type rotors are used in turbo-alternators and these are made up of solid steel forging to get high mechanical stress.
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Salient pole rotor
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Cylindrical rotor
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Large diameter and short axial length
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Small diameter and long axial length
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used for low-speed alternators
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Used for high-speed turbo alternators
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Has no projecting poles
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Has no projecting poles
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Needs damper windings
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Do not need damper windings
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Windage loss is more
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Windage loss is less
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As salient pole rotor has a large diameter and short axial length, length to diameter is ratio is very small.
As Non-salient pole type rotor has a small diameter and long axial length, length to diameter is ratio is very high.
