Efficiency of DC Generator & Condition for Maximum Efficiency

The power flow from 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 the efficiency of a generator is given as,

Condition for Maximum Efficiency :

Let,

• Generator output = VI
• Generator input = output + losses

=  VI + I_a2 R_a + W_c

 =  VI + I2 R_a  +  W_c

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

Efficiency,

η  =  power output /  power input

(By dividing Nr. and Dr. by VI)

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

Hence, the efficiency is maximum when,

VARIABLE LOSS  =  CONSTANT LOSS