Why is a shaft coupler used between turbine and generator ?

Why is a shaft coupler used between turbine and generator ?
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3 Answers

Answer :

first of all its necessary for doing maintenance second its easy to install turning gear motor for rotating the turbine shaft during its cooling down if the unit stopped for long time (that for thermal power stations)
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Answer :

To Carter for flexibility of shafts misalignment that can result from vibrations.
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Answer :

For easy transmission torque or rotation angle and can also use for the protection of the safety devices shaft cannot be separated from the shaft during motion coupling will be damaged first so as avoid to the damaged of motor or other transmission parts.
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