144 



ELEMENTS OF ELECTRICAL ENGINEERING. 



Draw the line ef, Fig. 125, through the point O making 

 with OC the angle 6 as shown, then Q, the projection of 

 OP on the line ef, represents the power output P tf of machine 

 B. This is shown as follows : The angle between B and E 

 is equal to 6 + (BI) and it is also equal to 6 plus the angle 



Fig. 125. 



POf, so that the angle POf is the same as the angle (BI). 

 Therefore 



OQ = OP cos (BI) = E cos (BI) = V&~+ X 2 /cos (BI) 



or 



*>- 



whence, substituting this value of /cos (BI) in equation (iv), we 

 have 



B-OQ 



P" = 



(v) 



