Introduction
                                  The function of a governor is to regulate the mean speed of an engine, when there are variations in the load e.g. 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.
                                             Types of Governors
The governors may, broadly, be classified as
1. Centrifugal governors, and 2. Inertia governors.
Classifications of the centrifugal governors

Watt Governor

Let m = Mass of the ball in kg,

w = Weight of the ball in newtons = m.g,

T = Tension in the arm in newtons,

ω = Angular velocity of the arm and ball about the spindle axis inrad/s,

r = Radius of the path of rotation of the ball i.e. horizontal distance

from the centre of the ball to the spindle axis in metres,

Fc = Centrifugal force acting on the ball in newtons = m.ω2.r, and

h = Height of the governor in metres.

ω = 2π N/60

h=895/N2

. (∵ g = 9.81 m/s2)

∴ Change in vertical height = h1 – h2

Porter Governor

The Porter governor is a modification of a Watt’s governor, with central load attached to the sleeve.

Let   m = Mass of each ball in kg,

                               w = Weight of each ball in newtons = m.g,

                 M = Mass of the central load in kg,

                                     W = Weight of the central load in newtons = M.g,

           r = Radius of rotation in metres,

            h = Height of governor in metres ,

     N = Speed of the balls in r.p.m .,

                                           ω = Angular speed of the balls in rad/s  = 2 πN/60 rad/s,

                                                Fc= Centrifugal force acting on the ball in newtons = m.ω2.r,

 T1 = Force in the arm in newtons,

T2 = Force in the link in newtons,

                                                    α = Angle of inclination of the arm (orupper link) to the vertical, and                                            β = Angle of inclination of the link(or lower link) to the vertical.