What type of coupling is used to connect turbines and the MG while allowing for slight misalignment?

Flexible coupling is specifically designed to accommodate slight misalignments between connected shafts, such as those found when connecting turbines to a motor-generator (MG) system. The primary function of a flexible coupling is to transmit torque while allowing for angular or axial misalignment that may occur during operation due to thermal expansion, vibration, or installation inaccuracies. This capability is crucial in applications involving turbines, where precise alignment may not always be feasible, ensuring smooth operation and preventing mechanical stress that could lead to premature failure.

In contrast, rigid couplings do not allow for any misalignment and are suited for applications where precise alignment can be maintained, which isn't typically the case in turbine scenarios. Semi-rigid couplings, while providing some flexibility, may not offer the same level of misalignment accommodation as flexible couplings. Universal joints allow for significant angular misalignment but are generally used in applications with varying shaft angles and are not specifically designed for the continuous torque transmission needed in turbine-MG setups. Thus, the flexibility offered by flexible couplings makes them the appropriate choice in this context.