GOVERNOR is an automatic device which regulates the speed of a prime mover so as to keep it within certain limits notwithstanding variations in the load or the pressure. The centrifugal governor is the principal type. It is made in numerous forms, all having two or more weights arranged so that they can freely move outwards upon increase of speed, or fall as speed falls. Any change of speed is communicated to the governor, which automatically varies the intake of power.
In steam engines the flow of steam is thus controlled, or ex pansion gear is actuated. In gas engines the full charge is ad mitted, but the governor shuts it off at excess speed, this system being termed the hit-and-miss. Or the volume of air and gas is varied, or the proportion of air to the gas, without, however, missing a charge. Oil and Diesel engines (q.v.) are governed by varying the quantity of fuel injected into the cylinders as the speed varies and affects the governor. Water turbines receive their governing from a curtailment of the supply by a movable sluice device or by a spear-head entering more or less deeply into an inlet cone. Elaborate governors are fitted to some steam tur bines, with a system of oil pressure to control the steam throttle valve. Governors for engines driving mine hoists operate a con trol unit arranged so that if the cage travels too fast the governor shuts off steam and applies the brakes automatically. It usually is necessary to arrange the governor mechanism so as to offer resistance to rapid movement or "hunting" may result.
A gas governor is used to regulate the pressure of gas supply, either at the works or on a small scale for gas cookers or gas fires. In the latter type of governor, weights on a spindle are regulated to suit the desired adjustment. (F. H. ; X.)