POWER LOSSES AND EFFICIENCY
The power losses in a de machine consists of input power that is converted into heat. Power losses occurring in a de machine are divided into
- copper or electrical losses
- iron or magnetic losses and
- mechanical losses as
Efficiency
The ratio of useful output to the total input is called the efficiency of the machine and is expressed as
Commercial or overall efficiency of a generator
Ng = Useful electrical power output
Total mechanical power input
Overall efficiency of a motor is given as
Efficiency will be maximum when variable losses are equal to constant losses. The load current corresponding to maximum
efficiency is given as IL =√Pc/Ra
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