Determination of Moment of Inertia (Cont.)

By Graphical Method:-

• In this method, apart from the speed vs. time curve, power (i.e., the rotational losses) vs. speed (from which the power vs. time curve can be plotted), are obtained and plotted to the same time axis.
  
  
• The area under the power vs. time is the kinetic energy used by the rotating masses during retardation.
  
  
• Moment of inertia can be worked out from the fact that:
  
  Area under the Power vs. time curve
  
  
  
  Where N is the normal rated speed.