Efficiency of DC Generator & Condition for Maximum Efficiency

The power flow input to output is known as power stages or power flow diagram

Efficiency :

     It may be defined as ' the ratio of output in watt (or KW) to the input in watt (or KW) '.

Mechanical efficiency,

Electrical efficiency,

Overall efficiency, η 'or' commercial efficiency, or

Efficiency of a generator, 

Condition for Maximum Efficiency :

Generator output  =  VI

Generator input  =  output  + losses
   

=  VI + I2 R_a + W_c

  

 =  VI + I2 R_a  +  W_c  

( assuming, I = I_a ; since I_sh is very small compared to I_a  )

Efficiency,

η  =  power output /  power input

Since dividing Nr and Dr by VI

     To obtain the maximum efficiency the denominator should be minimum, therefore differentiating the de-nominator with respect to I and equate to zero.

Hence, the efficiency is maximum when

  VARIABLE LOSS  =  CONSTANT LOSS