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_shis 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