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 + Ia2 Ra + Wc
= VI + I2 Ra + Wc
(assuming, Ia = I ; since Ish is very small compared to Ia )
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