The function of a governor is to regulate the mean speed of an engine, when there are variations in the load, eg. When the load on an engine increases, its speed decreases, therefore it becomes necessary to increase the supply of working fluid.

On the other hand, when the load on the engine decreases, its speed increases and thus less working fluid is required.

The governor automatically controls the supply of working fluid to the engine with the varying load conditions and keeps the mean speed within certain limits.