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 of DC Generator

Efficiency :

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


Mechanical efficiency,

Efficiency of DC Generator & Condition for Maximum Efficiency

Electrical efficiency,

Efficiency of DC Generator & Condition for Maximum Efficiency

Overall efficiency, η 'or' commercial efficiency, or the efficiency of a generator is given as,

Efficiency of DC Generator & Condition for Maximum Efficiency

Condition for Maximum Efficiency :

Let,
  • Generator output = VI
  • Generator input = output + losses
= VI + Ia2 Ra + Wc
= VI + I2 Ra + Wc
(assuming, Ia = I ; since Ishis very small compared to Ia)
Efficiency,
η = power output / power input
Efficiency of DC Generator & Condition for Maximum Efficiency
(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.

Efficiency of DC Generator & Condition for Maximum Efficiency

Hence, the efficiency is maximum when,

VARIABLE LOSS = CONSTANT LOSS

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