GOVERNORS 247 



is thus evident that the quicker the governor movement, the greater 

 the pressure rise will be, while, if the governor movement is made 

 slower, the speed increase will be greater, and a proper balance 

 between the two is, therefore, the correct time for adjusting the 

 governor closing stroke. Few conditions will, however, warrant 

 a stroke quicker than 1J seconds. 



In addition, the flywheel effect must be considered the greater 

 the inertia of the rotating masses and the higher their rotation, 

 the smaller the speed variation will be. A sufficient rotating mass 

 to supply stored energy (WR 2 ) must, therefore, also be intro- 

 duced to keep the speed within permissible limits. 



To secure a constant speed with a water wheel operated under 

 a variable load, the energy produced by the water wheel must be 

 varied proportionally to the load, and the method of achieving this 

 in practice, except for tangential impulse wheels with deflecting 

 nozzles, consists essentially of varying the size of the gate or valve 

 openings through which the water to the wheels is admitted (see 

 " Speed Regulation," page 220). 



The regulation of hydro-electric units, as stated, requires a 

 certain departure from normal speed before the governor can act. 

 Since the immediate effect of the gate motion is opposite to that 

 intended, the speed will depart still further from the normal, which, 

 in turn, tends to cause the governor to move the gate too far, with 

 the result that the speed will not only return to normal as soon as 

 the inertia of the water and the rotating parts is overcome, but 

 may rush far beyond normal in the opposite direction. 



A given gate opening will produce a certain velocity of the 

 water in the penstock and the energy of the moving water will be 

 equal to the weight of the water in the penstock multiplied by the 

 square of the velocity and dividing this product by 64.4. For 

 example, with a penstock 300 feet long and 6 feet in diameter, the 

 weight of the water would be 530,000 pounds, and assuming a 

 velocity of 5 feet per second, corresponding to the head and full 

 gate opening, the total kinetic energy of the water would be 



530,000X52 on( 

 64 4 = 205,752 foot-pounds. 



If the gates are now instantly closed to about one-quarter 

 gate opening so that the velocity would be reduced to 1.5 feet per 

 second, the corresponding kinetic energy would only be 18,517 



