what is the meaning of transformer short circuit test?

Answer Posted / amal

The short circuit test is performed by short circuiting one
of the two windings, by supplying the other one with a
voltage adjustable from zero, until reaching the value of
the rated current of the winding itself. The voltage
required at this purpose can be of the order from 4 to 10%
of the winding Vn on which we perform the power supply; such
a voltage is defined short circuit voltage of the
transformer. In this test, the whole absorbed power
corresponds to the only copper losses of the two windings,
since, the low applied voltage given (in the short circuit
test of the transformer), the magnetizing current, the flux
in the core and the consequent losses are negligible. In
these conditions we determine the equivalent resistance of
the transformer.
In turn we will therefore be able to determine the
variations of the secondary voltage that take place from no-
load to load condition of the transformer itself. Even in
this test it is indifferent to supply the primary or
secondary winding. In practice it is necessary to consider
that it is suitable that the involved currents reach the
tayed value of full load both in the side of the supply
winding and in the other short circuited one. The first
value will be necessary for the instrument choice, while the
second one for the choice of the cable section to be used on
the short circuit connections.

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