What role does an overrun clutch play in a power transmission system?

An overrun clutch plays a critical role in a power transmission system by allowing the output shaft to rotate freely when the driving shaft slows down. This functionality is particularly important in applications where deceleration may occur, such as in automotive applications or machinery that experiences variable loads.

When the driving shaft decelerates, the overrun clutch disengages, enabling the output shaft to continue rotating without resistance from the driving side. This prevents potential mechanical damage and ensures smoother operation by avoiding sudden stops that could lead to wear and tear on components.

In contrast, the other options describe functions that do not accurately represent the purpose of an overrun clutch. While preventing the output shaft from rotating would conflict with the idea of allowing free rotation, increasing torque is more characteristic of a gear mechanism rather than an overrun clutch. Stopping the system completely during failure would pertain to safety mechanisms or emergency stops rather than the function of this specific clutch type. Thus, understanding the specific role of an overrun clutch clarifies its importance in facilitating flexibility and efficiency within the power transmission system.