Page 563 - Basic Electrical Engineering
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circuit, the core loss component has been neglected. Thus, we can equate the
wattmeter reading to copper losses in the two windings. The short-circuit test
readings are taken by adjusting the voltage applied to the primary through a
variac, i.e., an auto transformer so that the rated current flows (to be noted
from the transformer name plate) through the windings. From the readings of
the three instruments, the following calculations are made.
W = Copper losses in the two windings having the rated current flowing
sc
through them.
From the data obtained from the no-load test and the short-circuit test, the
efficiency and regulation of a transformer can be calculated without actually
loading the transformer.
6.13 EFFICIENCY OF A TRANSFORMER
The whole input power to a transformer is not available at the output, some is
lost in the iron core as core loss and some is lost in the windings as copper
loss. Since the transformer is a static device, there is no friction and windage
loss (rotational loss) in the transformer.
Input = Output + Losses
